TC 3-09.81 Field Artillery Manual Cannon Gunnery APRIL 2016 DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. *This publication supersedes TC 3-09.81/MCWP 3-16.4, dated 1 March 2016. Headquarters, Department of the Army This publication is available at Army Knowledge Online (https://armypubs.us.army.mil/doctrine/index.html). To receive publishing updates, please subscribe at http://www.apd.army.mil/AdminPubs/new_subscribe.asp Training Circular No. 3-09.81 *TC 3-09.81 Headquarters Department of the Army Washington, DC, 13 April 2016 Field Artillery Manual Cannon Gunnery Contents CHAPTER 1 CHAPTER 2 CHAPTER 3 Page PREFACE.......................................................................................................... xxiii INTRODUCTION ................................................................................................xxv THE GUNNERY PROBLEM AND THE GUNNERY TEAM ............................... 1-1 Gunnery Problem Solution ................................................................................. 1-1 Field Artillery Gunnery Team.............................................................................. 1-1 Five Requirements For Accurate Fire ................................................................ 1-2 FIRING BATTERY AND BATTERY ORGANIZATION ..................................... 2-1 Battery Organization in the BCT......................................................................... 2-1 Battery or Platoon FDC ...................................................................................... 2-1 Relationship Between Battery or Platoon and Battalion FDC ............................ 2-2 Battalion FDC Personnel .................................................................................... 2-2 BALLISTICS ...................................................................................................... 3-1 Section I: Interior Ballistics ............................................................................. 3-1 Nature of Propellant and Projectile Movement................................................... 3-2 Factors Causing Nonstandard Velocities. .......................................................... 3-6 Section II: Transitional Ballistics .................................................................. 3-10 Section III: Exterior Ballistics ........................................................................ 3-10 Trajectory Elements.......................................................................................... 3-10 Trajectory in a Vacuum..................................................................................... 3-12 Trajectory in a Standard Atmosphere............................................................... 3-12 Relation of Air Resistance and Projectile Efficiency to Standard Range ......... 3-13 Deviations From Standard Conditions.............................................................. 3-14 Dispersion and Probability................................................................................ 3-15 Causes of Dispersion ....................................................................................... 3-15 Mean Point of Impact........................................................................................ 3-16 Probable Error .................................................................................................. 3-16 Dispersion Zones.............................................................................................. 3-17 Range Probable Error....................................................................................... 3-17 Distribution Restriction: Approved for public release; distribution is unlimited. *This publication supersedes TC 3-09.81/MCWP 3-16.4, dated 1 March 2016. i Contents CHAPTER 4 CHAPTER 5 Fork ................................................................................................................... 3-18 Deflection Probable Error.................................................................................. 3-18 Time-To-Burst Probable Error........................................................................... 3-18 Height-Of-Burst Probable Error......................................................................... 3-18 Range-To-Burst Probable Error ........................................................................ 3-18 Section IV: Terminal Ballistics....................................................................... 3-19 Target Analysis and Munition Effects (Weaponeering).....................................3-19 Determining Most Suitable Weapon and Ammunition ...................................... 3-24 Determining the Method of Attack..................................................................... 3-25 Predicting Weapons and Munitions Effects ...................................................... 3-26 Joint Munitions Effectiveness Manuals Weaponeering System (JWS) ...........3-26 Quick Reference Tables ................................................................................... 3-26 Munitions Effects............................................................................................... 3-30 MUZZLE VELOCITY MANAGEMENT ............................................................... 4-1 Section I: Muzzle Velocity Terms .................................................................... 4-1 Section II: Correction Tables and Forms........................................................ 4-4 Muzzle Velocity Correction Tables (MVCT) ........................................................ 4-4 DA Form 4982-1 M90 Velocimeter Work Sheet ................................................. 4-7 DA Form 4982 Muzzle Velocity Record .............................................................. 4-8 Section III: Techniques to Determine Muzzle Velocity Variations ............. 4-10 First Lot Calibration (Baseline Calibration). ...................................................... 4-10 Subsequent Lot Inferred Calibration. ................................................................ 4-11 Predictive Muzzle Velocity Technique. ............................................................. 4-11 Section IV: Examples of the Techniques Used to Determine Muzzle Velocity ............................................................................................................ 4-14 Complete M90 Velocimeter Work Sheet (DA Form 4982-1).............................4-14 Complete the Muzzle Velocity Record (DA Form 4982) ................................... 4-17 Subsequent Lot Inferred Calibration ................................................................. 4-18 Determination of Shooting Strength.................................................................. 4-21 Section V: Muzzle Velocity Management...................................................... 4-24 Transferring MVVs ............................................................................................ 4-25 Updating Propellant Efficiencies Data............................................................... 4-25 MVV Logbook.................................................................................................... 4-26 Frequency of Calibration ................................................................................... 4-27 FIRE MISSION MESSAGES .............................................................................. 5-1 Section I: Fire Order.......................................................................................... 5-1 Overview ............................................................................................................. 5-1 Target Attack Considerations.............................................................................. 5-1 Fire Order Elements............................................................................................ 5-2 Battery or Platoon Fire Order .............................................................................. 5-5 Fire Order Standard Operating Procedures (SOP)............................................. 5-9 Battalion Fire Order........................................................................................... 5-11 Massing of Fires ................................................................................................ 5-13 Section II: Message To Observer .................................................................. 5-16 Description ........................................................................................................ 5-16 Additional Information ....................................................................................... 5-17 ii TC 3-09.81 13 April 2016 Contents CHAPTER 6 Section III: Fire Commands ........................................................................... 5-18 Fire Command Elements.................................................................................. 5-18 Battery or Platoon Fire Commands .................................................................. 5-19 FIRING CHARTS ............................................................................................... 6-1 Section I: Explanation of Terms...................................................................... 6-1 Direction.............................................................................................................. 6-1 Mils ..................................................................................................................... 6-1 Degrees .............................................................................................................. 6-1 Cardinal Directions ............................................................................................. 6-1 Azimuth............................................................................................................... 6-2 Right Add, Left Subtract Rule (RALS) (For Determination of Azimuth) ............. 6-2 Deflection............................................................................................................ 6-2 Left Add, Right Subtract Rule (LARS) (For Determination of Deflection) .......... 6-2 Observer-Target Line ......................................................................................... 6-2 Gun-Target Line ................................................................................................. 6-2 Angle T ............................................................................................................... 6-2 Range/Distance .................................................................................................. 6-3 Section II: Types of Firing Charts ................................................................... 6-3 Description.......................................................................................................... 6-3 Firing Chart Construction.................................................................................... 6-3 Section III: Plotting Equipment and Firing Chart Preparation ..................... 6-4 Pencils ................................................................................................................ 6-4 Plotting Pins....................................................................................................... 6-4 Plotting Scale..................................................................................................... 6-5 Range-Deflection Protractor ............................................................................... 6-5 Target Grid.......................................................................................................... 6-6 Section IV: Surveyed Firing Chart .................................................................. 6-7 Selection of Lower Left-Hand Corner and Azimuth of Lay ...................................... 6-7 Firing Chart Preparation ..................................................................................... 6-8 Four-Step Plotting Method.................................................................................. 6-9 Tick Marks ........................................................................................................ 6-11 Construct North Indexes................................................................................... 6-14 Construction of Azimuth Indexes...................................................................... 6-17 Construction of Deflection Indexes................................................................... 6-19 Plotting Targets ................................................................................................ 6-24 Determining and Announcing Chart Data......................................................... 6-28 Section V: Observed Firing Chart ................................................................. 6-30 Overview........................................................................................................... 6-30 Methods of Determining Polar Plot Data .......................................................... 6-31 Constructing Observed Firing Charts ............................................................... 6-32 Determination of Direction for Polar Plotting .................................................... 6-33 Percussion Plot, VI Unknown ........................................................................... 6-36 Percussion Plot, VI Estimated .......................................................................... 6-36 Time Plot, VI Unknown ..................................................................................... 6-36 Time Plot, VI Known (Preferred Technique)..................................................... 6-37 Setting Up the Observed Firing Chart .............................................................. 6-40 13 April 2016 TC 3-09.81 iii Contents CHAPTER 7 CHAPTER 8 CHAPTER 9 Example of Percussion Plot, VI Unknown. ....................................................... 6-41 Example of Percussion Plot, VI Estimated ....................................................... 6-41 Example of Time Plot, VI Unknown .................................................................. 6-42 Example of Time Plot, VI Known, XO’s High Burst........................................... 6-43 Locate an Observer........................................................................................... 6-44 Battalion Observed Firing Charts ...................................................................... 6-44 Observed Firing Chart With Incomplete Survey ............................................... 6-46 Section VI: Using Map Spot Data to Construct Firing Charts .................... 6-46 Map Spot Survey............................................................................................... 6-46 Constructing a Firing Chart From Map Spot Survey......................................... 6-47 Transferring to a Surveyed Firing Chart............................................................ 6-47 FIRING TABLES................................................................................................. 7-1 Section I: Tabular Firing Table ........................................................................ 7-1 Elements and Purpose........................................................................................ 7-1 Cover Information................................................................................................ 7-2 Part 1................................................................................................................... 7-7 Illuminating Projectiles ...................................................................................... 7-24 Part 2................................................................................................................. 7-25 TFT Part 3 and Part 4 ....................................................................................... 7-25 Appendixes ....................................................................................................... 7-26 Section II: Graphical Firing Tables................................................................ 7-26 Overview ........................................................................................................... 7-26 Low-Angle GFTs ............................................................................................... 7-27 High-Angle GFT ................................................................................................ 7-29 Illuminating Projectile GFT ................................................................................ 7-30 SITE .................................................................................................................... 8-1 Initial Elements of the Trajectory......................................................................... 8-1 Site in High Angle Fire ........................................................................................ 8-2 Determination of Altitudes ................................................................................... 8-2 Determination of Site Using Manual Computations ............................................ 8-3 Determination of Vertical Angle .......................................................................... 8-4 The Graphical Site Table .................................................................................... 8-5 Determination of Angle of Site and Vertical Angle with the GST ........................ 8-7 Determination of Site with the GST..................................................................... 8-8 High Angle Site ................................................................................................... 8-9 Determining High-Angle Site with the 10-Mil Site Factor.................................... 8-9 Determining High-Angle Site with the TFT ....................................................... 8-10 Sample Problems.............................................................................................. 8-11 Average Site...................................................................................................... 8-15 FIRE MISSION PROCESSING........................................................................... 9-1 Section I: Duties and the Record of fire ......................................................... 9-1 Crew Duties for the FDC ..................................................................................... 9-1 Elements of Firing Data ...................................................................................... 9-3 Recording Firing Data ......................................................................................... 9-4 Section II: High Explosive .............................................................................. 9-11 Overview ........................................................................................................... 9-12 iv TC 3-09.81 13 April 2016 Contents Examples of Completing the Record of Fire for HE Fire Missions ................... 9-13 Section III: High Angle Fire............................................................................ 9-32 Duties of Personnel in High-Angle Fire ............................................................ 9-32 Example of Completing the ROF for an HE High-Angle Adjust-Fire Mission... 9-34 Section IV: Illumination.................................................................................. 9-37 Overview........................................................................................................... 9-37 Illumination Firing Data..................................................................................... 9-37 Determination of Illumination Firing Data with the GFT ................................... 9-38 Determination of Illumination Firing Data with the TFT .................................... 9-38 CHAPTER 10 REGISTRATION .............................................................................................. 10-1 Section I: Reasons for Registration ............................................................. 10-1 Accurate Firing Unit Location ........................................................................... 10-1 Accurate Weapon and Ammunition Information............................................... 10-1 Accurate Meteorological Information................................................................ 10-1 Accurate Computational Procedures................................................................ 10-2 When to Conduct Registrations........................................................................ 10-2 Types of Registrations...................................................................................... 10-2 Assurance Tables ............................................................................................. 10-4 Registration Corrections and GFT Settings...................................................... 10-4 Section II: Precision Registrations ............................................................... 10-5 Objective........................................................................................................... 10-5 Initiation of a Precision Registration ................................................................. 10-5 Conduct of the Impact Phase of a Precision Registration................................ 10-6 Conduct of the Time Phase of a Precision Registration................................... 10-7 Second Lot Registrations ................................................................................. 10-7 Initiation of the Second Lot Registration........................................................... 10-7 Abbreviated Precision Registration ................................................................ 10-13 Section III: High-Burst/Mean Point of Impact Registrations .................... 10-15 Description...................................................................................................... 10-15 Selecting an Orienting Point ........................................................................... 10-15 Orienting the Observers ................................................................................. 10-17 Determining Firing Data.................................................................................. 10-18 Firing the HB or MPI Registration................................................................... 10-18 Determine the Mean Burst Location ............................................................... 10-19 Determination of the MBL............................................................................... 10-24 Determination of Chart Data and Registration Corrections ............................ 10-31 Effect of Complementary Angle of Site on Adjusted Fuze Setting ................. 10-32 Section IV: Process a Radar Registration.................................................. 10-33 Characteristics ................................................................................................ 10-33 Conduct of a Radar Registration .................................................................... 10-34 Section V: High-Angle Registration............................................................ 10-38 High-Angle GFT.............................................................................................. 10-39 Procedures for High-Angle Impact Registration ............................................. 10-39 Computation of the Adjusted Elevation .......................................................... 10-39 Section VI: Offset Registrations or Registrations to the Rear................. 10-42 Offset Registration .......................................................................................... 10-42 13 April 2016 TC 3-09.81 v Contents Registrations to the Rear ................................................................................ 10-42 Section VII: Determination and Application of Regitration Corrections . 10-43 Computation of Total Range Correction ......................................................... 10-43 Computation of Total Fuze Correction ............................................................ 10-43 Computation of Total Deflection Correction .................................................... 10-44 Determination of Total Registration Corrections ............................................. 10-44 Low-Angle GFT Settings ................................................................................. 10-45 Determination of a GFT Setting When the Registering Piece is not the Base Piece ............................................................................................................... 10-46 Construction of a GFT Setting ........................................................................ 10-47 Construction of a Two-Plot or Multi-plot GFT Setting ..................................... 10-48 Construction of a GFT Setting From a M107 Registration on an Illuminating GFT ................................................................................................................. 10-50 Update of a GFT Setting When Transferring From a Map Spot or Observed Firing Chart ..................................................................................................... 10-50 Registration Transfer Limits ............................................................................ 10-51 High-Angle GFT Settings. ............................................................................... 10-53 High-Angle Transfer Limits ............................................................................. 10-53 Transfer of GFT Settings ................................................................................ 10-53 Example of Transferring a GFT Setting .......................................................... 10-55 CHAPTER 11 METEOROLOGICAL TECHNIQUES ............................................................... 11-1 Section I: Principles........................................................................................ 11-1 Purpose and Use of Met Techniques................................................................ 11-1 Met Messages ................................................................................................... 11-4 Section II: Derivation of Ballistic Data ........................................................ 11-10 The Need for Ballistic Data ............................................................................. 11-11 Atmospheric Structure and Standard Conditions............................................ 11-11 Density Weighting Factors .............................................................................. 11-13 Section III: Concurrent Met Technique ....................................................... 11-14 DA Form 4200 Met Data Correction Sheet ..................................................... 11-14 Solution of a Concurrent Met .......................................................................... 11-16 Section IV: Subsequent Met Applications .................................................. 11-40 Overview ......................................................................................................... 11-40 Met to Met Check Gauge Point ....................................................................... 11-40 Met to a Target................................................................................................ 11-52 Met + VE ......................................................................................................... 11-53 CHAPTER 12 TERRAIN GUN POSITION CORRECTIONS & SPECIAL CORRECTIONS ... 12-1 Section I: Types of Corrections..................................................................... 12-1 Overview ........................................................................................................... 12-1 Howitzers Displacement ................................................................................... 12-2 Sheafs ............................................................................................................... 12-3 Section II: The M17/M19 Plotting Board ....................................................... 12-5 M19 Plotting Board............................................................................................ 12-5 M17 Plotting Board............................................................................................ 12-7 Section III: Terrain Gun Position Corrections ............................................ 12-16 Transfer Limits and Sectors of Fire................................................................. 12-16 vi TC 3-09.81 13 April 2016 Contents Fire Order and Fire Commands...................................................................... 12-17 Determination of Terrain Gun Position Corrections ....................................... 12-17 Hasty Terrain Gun Position Corrections ......................................................... 12-22 Determination of Hasty TGPCs ...................................................................... 12-22 Section IV: Special Corrections .................................................................. 12-26 Definitions and Use ........................................................................................ 12-26 Computation of Special Corrections ............................................................... 12-26 Section V: Use of Plotting Board for Fire Mission Processing................ 12-30 Fire Mission Processing with the M17 Plotting Board .................................... 12-30 Determination of Subsequent Corrections for a Laser Adjust-Fire Mission ... 12-31 Examples of TGPCs ....................................................................................... 12-33 Examples of Special Corrections ................................................................... 12-37 CHAPTER 13 SPECIAL MUNITIONS..................................................................................... 13-1 Section I: Rocket-Assisted Projectile........................................................... 13-1 Description........................................................................................................ 13-1 Manual Computations....................................................................................... 13-1 Registration and Determining a GFT Setting ................................................... 13-2 Section II: Smoke Projectiles ........................................................................ 13-6 Description........................................................................................................ 13-6 Employment...................................................................................................... 13-6 Quick Smoke .................................................................................................... 13-7 M825 Smoke Procedures ............................................................................... 13-15 M825 Examples .............................................................................................. 13-16 Section III: Dual-Purpose Improved Conventional Munitions.................. 13-19 Overview......................................................................................................... 13-19 Determining DPICM Firing Data ..................................................................... 13-19 Section IV: Family of Scatterable Mines .................................................... 13-24 Types of Scatterable Mines ............................................................................ 13-24 FASCAM Tactical Considerations and Fire Order Process ........................... 13-25 Technical Fire Direction Procedures .............................................................. 13-34 ADAM ............................................................................................................. 13-36 RAAMS ........................................................................................................... 13-37 DA Form 5032 ................................................................................................ 13-37 Safety Zone Determination............................................................................. 13-42 FASCAM Employment Steps ......................................................................... 13-44 Section V: Base Burn DPICM ...................................................................... 13-46 Base Burn DPICM (M864).............................................................................. 13-47 M864 Firing Data Computations..................................................................... 13-47 CHAPTER 14 EMERGENCY FDC PROCEDURES ............................................................... 14-1 Methods of Determining Initial Data ................................................................. 14-1 Methods of Determining Subsequent Data ...................................................... 14-2 Emergency Firing Chart.................................................................................... 14-2 M19 or M17 Plotting Board............................................................................... 14-8 Emergency Firing Chart Example .................................................................. 14-10 CHAPTER 15 SAFETY............................................................................................................ 15-1 13 April 2016 TC 3-09.81 vii Contents Section I: Responsibilities and Duties.......................................................... 15-1 Responsibilities ................................................................................................. 15-1 Duties of Safety Personnel ............................................................................... 15-2 Safety Aids ........................................................................................................ 15-4 Section II: Manual Computations of Safety Data ......................................... 15-5 Manual Computational Procedures................................................................... 15-5 Range Safety Card............................................................................................ 15-6 Basic Safety Diagram........................................................................................ 15-6 Computation of Low Angle Safety Data ............................................................ 15-8 Safety T ........................................................................................................... 15-12 Updating Safety Data after Determining a GFT Setting..................................15-13 Determination of Maximum Effective Illumination Area .................................. 15-22 Safety Considerations for M549/M549A1 RAP............................................... 15-23 Safety Considerations for M864 Base Burn DPICM/M795A1 Base Burn HE. 15-23 Computation of High Angle Safety.................................................................. 15-23 Section III: Minimum Quadrant Elevation ................................................... 15-30 Elements of Computation................................................................................ 15-30 Measuring Angle of Site to Crest .................................................................... 15-31 Measuring Piece-To-Crest Range .................................................................. 15-31 Computation of Fuzes Other Than Armed VT ................................................ 15-31 Using Minimum Quadrant Elevation ............................................................... 15-34 Intervening Crest............................................................................................. 15-34 APPENDIX A BATTERY OR PLATOON FIRE DIRECTION CENTER SOP .......................... A-1 APPENDIX B TROUBLESHOOTING....................................................................................... B-1 APPENDIX C PLANNING RANGES ........................................................................................ C-1 APPENDIX D REPLOT PRCEDURES ..................................................................................... D-1 APPENDIX E AUTOMATED FDC............................................................................................ E-1 APPENDIX F DETERMINING DATA........................................................................................F-1 APPENDIX G SPECIAL SITUATIONS..................................................................................... G-1 APPENDIX H SMOKE TABLES............................................................................................... H-1 GLOSSARY .......................................................................................... Glossary-1 REFERENCES.................................................................................. References-1 INDEX ......................................................................................................... Index-1 Figures Figure 3-1. Cannon Tube. ...................................................................................................... 3-2 Figure 3-2. Separate Loading 155mm Projectile. .................................................................. 3-3 Figure 3-3. Initial Excessive Pressure.................................................................................... 3-5 Figure 3-4. Delayed Excessive Pressure............................................................................... 3-6 Figure 3-5. Desirable Pressure Travel Curve. ....................................................................... 3-6 Figure 3-6. Velocity Changes................................................................................................. 3-7 viii TC 3-09.81 13 April 2016 Contents Figure 3-7. Intrinsic Elements of the Trajectory.................................................................... 3-10 Figure 3-8. Initial Elements of the Trajectory........................................................................ 3-11 Figure 3-9. Terminal Elements of the Trajectory. ................................................................. 3-12 Figure 3-10. Trajectories in a Standard Atmosphere and in a Vacuum. .............................. 3-13 Figure 3-11. Dispersion Rectangle. ...................................................................................... 3-16 Figure 3-12. Probable Errors. ............................................................................................... 3-17 Figure 3-13. Dispersion Zones. ............................................................................................ 3-17 Figure 3-14. Comparison of PEHB, PERB, and PETB.............................................................. 3-19 Figure 3-15. Determining the Precedence of Attack. ........................................................... 3-20 Figure 3-16. Attack Guidance Matrix Example..................................................................... 3-21 Figure 3-17. Weapon-Ammunition Selection........................................................................ 3-24 Figure 3-18. Considerations in Selecting a Method of Attack. ............................................. 3-25 Figure 3-19. APICM grenades.............................................................................................. 3-31 Figure 3-20. 155-mm DPICM grenade. ................................................................................ 3-32 Figure 3-21. RAAMS mine.................................................................................................... 3-33 Figure 3-22. ADAM mine. ..................................................................................................... 3-34 Figure 4-1. Comparative and Absolute Calibration results..................................................... 4-2 Figure 4-2. Section Cover and Standard MV Example. ......................................................... 4-6 Figure 4-3. Correction Table Charge 4H M232A1, for M107 Projectile Family...................... 4-7 Figure 4-4. M90 Velocimeter Work Sheet. ............................................................................. 4-8 Figure 4-5. Muzzle Velocity Record. ...................................................................................... 4-9 Figure 4-6. Digital Weapon Record Data. ............................................................................ 4-12 Figure 4-7. MACS Propellant Efficiencies (PE) Example. .................................................... 4-13 Figure 4-8. M90 Velocimeter Worksheet Example............................................................... 4-15 Figure 4-9. DA Form 4982 Muzzle Velocity Record for a first lot calibration. ...................... 4-17 Figure 4-10. M90 Velocimeter Work Sheet for Second-Lot Inferred Calibration.................. 4-19 Figure 4-11. Muzzle Velocity Record for Second-Lot Inferred Calibration. .......................... 4-20 Figure 4-12. Approximate Losses in Muzzle Velocity. ......................................................... 4-21 Figure 4-13. Equivalent Full Service Rounds Table ............................................................. 4-22 Figure 4-14. Approximate Losses in Muzzle Velocity .......................................................... 4-23 Figure 4-15. MACS Propellant Efficiencies (PE) Example ................................................... 4-24 Figure 4-16. Muzzle Velocity Record for a First Lot Calibration, Line 5. .............................. 4-26 Figure 4-17. Muzzle Velocity Record Remarks Block. ......................................................... 4-26 Figure 4-18. Muzzle Velocity Variation (MVV) Logbook Major Tabs.................................... 4-27 Figure 4-19. Muzzle Velocity Variation (MVV) Logbook Tabs.............................................. 4-27 Figure 5-1. Fire Order Elements............................................................................................. 5-2 Figure 5-2. Sheaf Distributions. .............................................................................................. 5-4 Figure 5-3. FDC Fire Order SOP.......................................................................................... 5-10 Figure 5-4. Example Fire Order............................................................................................ 5-11 Figure 5-5. Example Battalion Fire Order SOP. ................................................................... 5-12 Figure 5-6. Example Battalion Fire Order............................................................................. 5-15 13 April 2016 TC 3-09.81 ix Contents Figure 5-7. Example Units to Fire. ....................................................................................... 5-16 Figure 5-8. Example Changes or additions to the CFF. ...................................................... 5-16 Figure 5-9. Example Number of Rounds. ............................................................................ 5-17 Figure 5-10. Example Target Number. ................................................................................ 5-17 Figure 5-11. Fire Command Example Adjust Fire. .............................................................. 5-24 Figure 5-12. Fire Command Example Fire for Effect. .......................................................... 5-25 Figure 5-13. Fire Command SOP Example. ........................................................................ 5-25 Figure 6-1. Cardinal directions. .............................................................................................. 6-1 Figure 6-2. The 6H Pencil (Wedge Point). ............................................................................. 6-4 Figure 6-3. The 4H Pencil (Conical Point). ............................................................................ 6-4 Figure 6-4. Plotting Scale....................................................................................................... 6-5 Figure 6-5. Range-Deflection Protractor. ............................................................................... 6-6 Figure 6-6. Labeling the Target Grid. ..................................................................................... 6-7 Figure 6-7. LLHC 2040, With the Long Axis Oriented East-West.......................................... 6-9 Figure 6-8. Position Plotted in Grid Square 2341. ............................................................... 6-10 Figure 6-9. Easting 2345...................................................................................................... 6-10 Figure 6-10. Northing 4184. ................................................................................................. 6-11 Figure 6-11. Dimensions of a Completed Tick Mark............................................................ 6-12 Figure 6-12. Canted Tick Marks........................................................................................... 6-12 Figure 6-13. Examples of Different Tick Marks.................................................................... 6-13 Figure 6-14. Constructing North Index Step1. ..................................................................... 6-14 Figure 6-15. Constructing North Index Step 2. .................................................................... 6-15 Figure 6-16. Constructing North Index Step 3. .................................................................... 6-16 Figure 6-17. Constructing North Index Step 4. .................................................................... 6-16 Figure 6-18. Labeling the RDP. ........................................................................................... 6-17 Figure 6-19. Orienting the RDP. .......................................................................................... 6-18 Figure 6-20. Constructing an Azimuth Index. ...................................................................... 6-19 Figure 6-21. Range-deflection Protractor Oriented East. .................................................... 6-20 Figure 6-22. Range-deflection Protractor Oriented on Azimuth of Lay................................ 6-21 Figure 6-23. Range-Deflection Protractor Oriented on Common Deflection. ...................... 6-22 Figure 6-24. Deflection Index. .............................................................................................. 6-23 Figure 6-25. Deflection Indexes for 6400 mils. .................................................................... 6-24 Figure 6-26. Polar Plot the Target Location. ........................................................................ 6-25 Figure 6-27. Orienting the Target Grid................................................................................. 6-26 Figure 6-28. Orienting the Target Grid (Continued). ............................................................ 6-27 Figure 6-29. Re-orienting the Target Grid on Initial Target Location. .................................. 6-27 Figure 6-30. Determining Angle T (Head-to-Head).............................................................. 6-29 Figure 6-31. Determining Angle T (Tail-to-Tail). .................................................................. 6-29 Figure 6-32. Observed Firing Chart Grid. ............................................................................ 6-31 Figure 6-33. Completed Record of Fire. .............................................................................. 6-35 Figure 6-34. Difference in Range Resulting from Difference in Vertical Interval. ................ 6-37 x TC 3-09.81 13 April 2016 Contents Figure 6-35. Comparison between the Adjusted QE and EL + CAS.................................... 6-38 Figure 6-36. GOT MINUS ASKED FOR Diagram. ............................................................... 6-40 Figure 6-37. Location of Batteries in Relation to the Known Point....................................... 6-45 Figure 7-1. Standard Conditions............................................................................................. 7-1 Figure 7-2. Symbols and Abbreviations. ................................................................................ 7-2 Figure 7-3. Interchangeability of Ammunition Tables. ............................................................ 7-3 Figure 7-4. Weapon Characteristics....................................................................................... 7-4 Figure 7-5. Projectile-Fuze Combinations and Mean Weights............................................... 7-4 Figure 7-6. Equivalent Full Service Rounds Table. ................................................................ 7-5 Figure 7-7. Approximate Losses in Muzzle Velocity Table. ................................................... 7-6 Figure 7-8. Charge Selection Table. ...................................................................................... 7-7 Figure 7-9. Conversion Factors. ............................................................................................. 7-7 Figure 7-10. Table A. .............................................................................................................. 7-8 Figure 7-11. Table B. .............................................................................................................. 7-9 Figure 7-12. Table C............................................................................................................. 7-10 Figure 7-13. Table D............................................................................................................. 7-11 Figure 7-14. Table E. ............................................................................................................ 7-11 Figure 7-15. Table F. ............................................................................................................ 7-13 Figure 7-16. Table G. ........................................................................................................... 7-17 Figure 7-17. Table H (Explanation – Firing East). ................................................................ 7-18 Figure 7-18. Table H (Explanation – Firing West). ............................................................... 7-19 Figure 7-19. Table H............................................................................................................. 7-20 Figure 7-20. Table I (0 Degrees Latitude). ........................................................................... 7-21 Figure 7-21. Table J. ............................................................................................................ 7-23 Figure 7-22. Table K. ............................................................................................................ 7-24 Figure 7-23. Graphical Firing Table...................................................................................... 7-26 Figure 7-24. GFT Label. ....................................................................................................... 7-27 Figure 7-25. High Angle GFT. .............................................................................................. 7-29 Figure 7-26. Illuminating Projectile M485 GFT, Charge 1L. ................................................. 7-30 Figure 7-27. Trajectory of an Illuminating Projectile M485, Charge 1L. ............................... 7-31 Figure 8-1. Elements of a Trajectory. ..................................................................................... 8-2 Figure 8-2. Vertical Angle. ...................................................................................................... 8-5 Figure 8-3. Graphical Site Table. ........................................................................................... 8-6 Figure 8-4. Range Changeover Graph. .................................................................................. 8-7 Figure 8-5. Magic T. ............................................................................................................... 8-7 Figure 8-6. ∡SI and VA using the GST. ............................................................................... 8-13 Figure 8-7. SI using the GST................................................................................................ 8-14 Figure 8-8. Average Site....................................................................................................... 8-16 Figure 9-1. Flow of Information between the Gunnery Team................................................. 9-1 Figure 9-2. DA Form 4504 Record of Fire. ............................................................................. 9-5 Figure 9-3. Call for Fire Block................................................................................................. 9-6 13 April 2016 TC 3-09.81 xi Contents Figure 9-4. Upper Computational Space and Related Data Blocks. ..................................... 9-7 Figure 9-5. Fire Order and Initial Fire Commands Block. ...................................................... 9-8 Figure 9-6. Message to Observer Block. ............................................................................... 9-9 Figure 9-7. Fire Planning and Observer Subsequent Corrections Block............................... 9-9 Figure 9-8. Subsequent Fire Commands Block. .................................................................. 9-10 Figure 9-9. Lower Computational Space and Administrative Blocks................................... 9-11 Figure 9-10. Fire Order SOP and Fire Command Standards. ............................................. 9-13 Figure 9-11. Example Record of Fire for an HE/Q Adjust-Fire Mission. .............................. 9-17 Figure 9-12. Determination of a 20 Meter Height of Burst for Time Fuze............................ 9-18 Figure 9-13. Effect of ▲FS on Achieved HOB. ................................................................... 9-18 Figure 9-14. Example of USDA Rule. .................................................................................. 9-19 Figure 9-15. Example Record of Fire for an HE/TI (M767) Adjust-Fire Mission. ................. 9-21 Figure 9-16. Example Record of Fire for an HE/TI (M767) FFE Mission............................. 9-24 Figure 9-17. Example Record of Fire for an HE/VT Adjust-Fire Mission. ............................ 9-26 Figure 9-18. Example Record of Fire for an HE/VT FFE Fire Mission. ............................... 9-28 Figure 9-19. Example Record of Fire for an HE Adjust-Fire Mission with WP/Q in Effect................................................................................................................. 9-31 Figure 9-20. High Angle Fire. ............................................................................................... 9-32 Figure 9-21. High-Angle Side Spray Compared to Low-Angle Side Spray. ........................ 9-33 Figure 9-22. Example Record of Fire for an HE High-Angle Adjust-Fire Mission................ 9-36 Figure 9-23. Employment Factors for Illuminating Projectiles. ............................................ 9-38 Figure 9-24. Example Record of Fire for a One-Gun Illumination Fire Mission................... 9-41 Figure 9-25. Example Record of Fire for a Two-Gun Illumination Range Spread Fire Mission.............................................................................................................. 9-44 Figure 9-26. Example ROF for a Four-Gun Illumination Range and Lateral Spread Fire Mission. ..................................................................................................... 9-46 Figure 9-27. Determination of Firing Interval for a Coordinated Illumination Mission.......... 9-47 Figure 9-28. Example ROF for the Illumination Portion of a Coordinated Illumination Fire Mission. ..................................................................................................... 9-48 Figure 9-29. Example ROF for the HE Portion of a Coordinated Illumination Fire Mission.............................................................................................................. 9-49 Figure 9-30. Example Record of Fire for a High-Angle Illumination Fire Mission................ 9-51 Figure 10-1. Registration Decision Diagram. ....................................................................... 10-3 Figure 10-2. Difference between Aiming Point and Surveyed Location. ............................. 10-6 Figure 10-3. ROF for a Precision Registration................................................................... 10-12 Figure 10-4. ROF for an Abbreviated Precision Registration. ........................................... 10-14 Figure 10-5. Apex Angle. ................................................................................................... 10-16 Figure 10-6. Example Message to Observer on DA Form 4201. ...................................... 10-17 Figure 10-7. 8 PER x 8 PED Rectangle for HB Registration. .............................................. 10-19 Figure 10-8. Observers’ Measured Azimuths. ................................................................... 10-20 Figure 10-9. Completed ROF for a HB Registration. ......................................................... 10-23 Figure 10-10. Aid for Determining the MBL Altitude. ......................................................... 10-24 xii TC 3-09.81 13 April 2016 Contents Figure 10-11. Completed DA Form 4201 for the Graphic Intersection Technique............. 10-26 Figure 10-12. Completed DA Form 4201 for the Polar Plot Technique. ............................ 10-27 Figure 10-13. Formula for Computing Distance to the MBL............................................... 10-28 Figure 10-14. Completed DA Form 4201 for the Grid Coordinates Technique.................. 10-30 Figure 10-15. Projectile Tracking—Target Acquisition Radar. ........................................... 10-35 Figure 10-16. Completed ROF for a HB Radar Registration.............................................. 10-37 Figure 10-17. Completed DA Form 4201 for a HB Radar Registration.............................. 10-38 Figure 10-18. Completed ROF of a High-Angle Impact Registration. ................................ 10-41 Figure 10-19. Offset Registration Data............................................................................... 10-42 Figure 10-20. A Completed Lazy Z. ................................................................................... 10-44 Figure 10-21. GFT with a GFT Setting Applied. ................................................................. 10-48 Figure 10-22. GFT with a Two Plot GFT Setting Applied. .................................................. 10-49 Figure 10-23. Deflection Transfer Limits—10,000 Meters or Less..................................... 10-52 Figure 10-24. Deflection Transfer Limits—Ranges Greater Than 10,000 Meters. ............ 10-52 Figure 10-25. GFT Setting for Battery A, 1st Platoon (Example). ....................................... 10-55 Figure 10-26. GFT Setting for Battery C, 1st Platoon (Example)........................................ 10-55 Figure 11-1. Standard Conditions. ....................................................................................... 11-1 Figure 11-2. Global Octants. ................................................................................................ 11-6 Figure 11-3. Introduction of the Computer MET Message. .................................................. 11-6 Figure 11-4. Zone Number Codes for Computer MET Messages. ...................................... 11-7 Figure 11-5. Completed DA Form 3677. .............................................................................. 11-8 Figure 11-6. Computer MET Message Errors. ................................................................... 11-10 Figure 11-7. Atmospheric Structure of Met Messages. ...................................................... 11-12 Figure 11-8. Standard Conditions for Weather................................................................... 11-13 Figure 11-9. Density Weighting Factors for Lines 00-09.................................................... 11-13 Figure 11-10. Completed ROF for a Precision Registration............................................... 11-25 Figure 11-11. DA Form 4200 Containing Known Data....................................................... 11-26 Figure 11-12. Table B. ........................................................................................................ 11-27 Figure 11-13. Computer Met Message Valid at the Time of the Registration. ................... 11-28 Figure 11-14. DA Form 4200 With Met Message Data Recorded. .................................... 11-29 Figure 11-15. Table C......................................................................................................... 11-30 Figure 11-16. Table D......................................................................................................... 11-30 Figure 11-17. DA Form 4200 With Tables A Through E Completed.................................. 11-31 Figure 11-18. Table E. ........................................................................................................ 11-32 Figure 11-19. Interpolation. ................................................................................................ 11-32 Figure 11-20. Table F. ........................................................................................................ 11-33 Figure 11-21. DA Form 4200 with Data from Table F Complete........................................ 11-34 Figure 11-22. Table H......................................................................................................... 11-35 Figure 11-23. DA Form 4200 With Position VE and Position Deflection Determined. ....... 11-36 Figure 11-24. Table I. ......................................................................................................... 11-37 Figure 11-25. Table J. ........................................................................................................ 11-38 13 April 2016 TC 3-09.81 xiii Contents Figure 11-26. Completed DA Form 4200 Containing the Concurrent Met. ....................... 11-39 Figure 11-27. Valid Computer Met Message. .................................................................... 11-47 Figure 11-28. DA Form 4200 with Known Data for a Met to Met Check Gauge Point. ..... 11-48 Figure 11-29. DA Form 4200 with Total Deflection and Total Range Corrections. ........... 11-49 Figure 11-30. Completed DA Form 4200 Containing the Met to Met Check Gauge Point Eight Direction Met. ............................................................................... 11-50 Figure 11-31. Octants. ....................................................................................................... 11-51 Figure 12-1. Maximum Advantage of Cover and Concealment........................................... 12-1 Figure 12-2. Howitzer Displacement.................................................................................... 12-3 Figure 12-3. Changes in the Sheaf Caused by a Change in the Line of Fire. ..................... 12-4 Figure 12-4. Projectile Effective Burst Widths and Open Sheaf Widths. ............................. 12-5 Figure 12-5. M19 Plotting Board. ......................................................................................... 12-6 Figure 12-6. The Vernier Scale. ........................................................................................... 12-7 Figure 12-7. M17 Plotting Board. ......................................................................................... 12-8 Figure 12-8. M17 Plotting Board With the Aiming Circle and Base Piece Plotted............. 12-12 Figure 12-9. M17 Plotting Board with All Howitzers Plotted, Azimuth Index Established, and Deflection Scale Continued for the M100-Series Sight. ..... 12-13 Figure 12-10. M17 Plotting Board with all Howitzers Plotted, Azimuth Index Established, and Deflection Scale Continued for the M12-Series Sight. ....... 12-15 Figure 12-11. TGPC Transfer Limits.................................................................................. 12-17 Figure 12-12. Three Sectors with Different Ranges and Overlapping for Different Charges. ......................................................................................................... 12-17 Figure 12-13. DA Form 4757 (Front and Back). ................................................................ 12-25 Figure 12-14. Format for Processing Fire Mission with M17. ............................................ 12-32 Figure 12-15. Completed DA Form 4757 Containing TGPCs for a Converged Sheaf. ..... 12-34 Figure 12-16. Completed DA Form 4757 Containing TGPCs for an Open Sheaf. ............ 12-35 Figure 12-17. Completed DA Form 4757 Containing TGPCs for a Circular Sheaf. .......... 12-36 Figure 12-18. Completed DA Form 4757 Containing Special Corrections. ....................... 12-38 Figure 12-19. M17 Plotting Board Oriented on an Attitude 1300, with a Target and Burst Point Plotted. ......................................................................................... 12-39 Figure 12-20. M17 Plotting Board Oriented on the Chart Deflection. ................................ 12-40 Figure 12-21. Completed DA Form 4757 Containing Special Corrections. ....................... 12-42 Figure 12-22. M17 Plotting Board With Both Grids Plotted. .............................................. 12-43 Figure 12-23. M17 Plotting Board With Burst Points Plotted. ............................................ 12-44 Figure 12-24. M17 Plotting Board Oriented on the Chart Deflection. ................................ 12-45 Figure 13-1. Valid Computer Met Message (RAP Fire Mission).......................................... 13-3 Figure 13-2. Completed Met Data Correction Sheet (RAP Fire Mission). ........................... 13-4 Figure 13-3. Completed Record of Fire (RAP Fire Mission). ............................................... 13-5 Figure 13-4. Completed ROF for Shell M825A1, Using a 155-AM-3 GFT with Supplementary M825A1 Scales. .................................................................... 13-17 Figure 13-5. Completed ROF for Shell M825A1, Using a 155-AM-3 GFT with Addendum T-2................................................................................................ 13-18 xiv TC 3-09.81 13 April 2016 Contents Figure 13-6. Completed ROF for Shell M483A1 using a 155-AM-3 GFT with Supplementary M483A1 Scales and a GFT Setting Applied. ......................... 13-22 Figure 13-7. Completed ROF for Shell M483A1 using a 155-AM-3 GFT with a GFT Setting Applied and Addendum R-3. .............................................................. 13-23 Figure 13-8. ADAM Projectile. ............................................................................................ 13-24 Figure 13-9. RAAMS Projectile........................................................................................... 13-25 Figure 13-10. Module Size 400 x 400 – Even Number of Aimpoints. ................................ 13-30 Figure 13-11. Module Size 400 x 400 – Odd Number of Aimpoints................................... 13-30 Figure 13-12. Module Size 200 x 200 – Even Number of Aimpoints. ................................ 13-30 Figure 13-13. Module Size 200 x 200 – Odd Number of Aimpoints................................... 13-30 Figure 13-14. Segmenting a Large FASCAM Target. ........................................................ 13-34 Figure 13-15. Target Grid Oriented on the Direction of Wind. ........................................... 13-35 Figure 13-16. Target Grid Reoriented Over Offset Point Aligned on the Attitude. ............. 13-36 Figure 13-17. Field Artillery Delivered Minefield Planning Sheet. ...................................... 13-38 Figure 13-18. Reverse Field Artillery Delivered Minefield Planning Sheet. ....................... 13-39 Figure 13-19. Field Artillery Mine Safety Template. ........................................................... 13-44 Figure 13-20. Base Burner DPICM (M864). ....................................................................... 13-47 Figure 14-1. Range-Azimuth Fan. ........................................................................................ 14-1 Figure 14-2. Platoon Location. ............................................................................................. 14-5 Figure 14-3. Common Deflection 3200. ............................................................................... 14-6 Figure 14-4. RDP With the Target Grid Oriented. ................................................................ 14-7 Figure 14-5. Target Grid Oriented on Observer Direction. ................................................... 14-8 Figure 15-1. Example of a Range Safety Card .................................................................... 15-6 Figure 15-2. Example of a Completed Safety Diagram, HE/WP.......................................... 15-8 Figure 15-3. Low Angle Safety Matrix. ............................................................................... 15-11 Figure 15-4. Completed Low Angle Safety Matrix, HE/WP................................................ 15-12 Figure 15-5. Example of a Completed Safety T. ................................................................ 15-13 Figure 15-6. Updated Low Angle Safety, GFT Setting Applied, HE/WP............................ 15-16 Figure 15-7. Example of Low Angle Safety Utilizing ADD-AD-1, M825A1......................... 15-17 Figure 15-8. Example of Initial Low Angle Safety, Shell Illum............................................ 15-18 Figure 15-9. Example of Low Angle Safety with Range K, Shell Illum............................... 15-19 Figure 15-10. Range Safety Card for Low Angle Safety with a Muzzle Velocity Correction, Shell HE/WP................................................................................. 15-20 Figure 15-11. Example of Low Angle Safety with a Muzzle Velocity Correction................ 15-21 Figure 15-12. High Angle Safety Matrix. ............................................................................ 15-26 Figure 15-13. Example of Initial High Angle Safety, Shell HE/WP..................................... 15-27 Figure 15-14. Example of Initial High Angle Safety Utilizing ADD-AD-1, Shell M825A1. .......................................................................................................... 15-28 Figure 15-15. Example of Initial High Angle Safety, Shell Illum. ........................................ 15-29 Figure 15-16. Angles of Minimum QE. ............................................................................... 15-31 Figure 15-17. Armed VT Decision Tree.............................................................................. 15-33 13 April 2016 TC 3-09.81 xv Contents Figure A-1. Internal Top View of Battery FDC in an M1068 Command Post Vehicle and SICP. ........................................................................................................... A-8 Figure A-2. Internal Top View of Battery FDC in HMMWV (for SICP, see Fig A-1). ............. A-9 Figure B-1. Howitzer Standard Muzzle Velocity. ................................................................... B-1 Figure B-2. Computer or Automated Systems Accounting for a Negative Muzzle Velocity. .............................................................................................................. B-2 Figure B-3. Troubleshooting Matrix........................................................................................ B-2 Figure B-4. Site Error. ............................................................................................................ B-5 Figure B-5. ORSTA Error DOF 1600. .................................................................................... B-6 Figure B-6. ORSTA Error DOF 6400. .................................................................................... B-6 Figure B-7. ORSTA Error DOF 0800. .................................................................................... B-7 Figure B-8. AOL Error. ........................................................................................................... B-8 Figure B-9. Projectile Square Weight Error............................................................................ B-9 Figure B-10. Propellant Temperature Error. ........................................................................ B-10 Figure B-11. MVV Error........................................................................................................ B-11 Figure B 12. Deflection Error. .............................................................................................. B-12 Figure B-13. Quadrant Error. ............................................................................................... B-13 Figure B-14. Charge Error. .................................................................................................. B-14 Figure D-1. Initial Target Location.........................................................................................D-2 Figure D-2. Observer’s Final Correction. .............................................................................. D-2 Figure D-3. Example Completed Record of Fire for Replot with Fuze PD. ..........................D-4 Figure D-4. Time Replot........................................................................................................D-5 Figure D-5. Example of a Completed ROF for Replot With Fuze Time (Deviation, Range, and HOB Refinement). ..........................................................................D-9 Figure E-1. Sample Record of Fire for Automated Fire Mission Processing. ........................ E-4 Figure F-1. Example Record of Fire for Adjust-Fire Mission with Fuze VT I/E Using a GFT Setting. ....................................................................................................... F-7 Figure F-2. Example of Completed Record of Fire for an AF Mission with Shell DPICM I/E........................................................................................................... F-9 Figure F-3. Example of Completed Record of Fire for a High-Angle FFE Mission with Fuze VT (GFT Setting Applied). ....................................................................... F-11 Figure F-4. Example of Completed Record of Fire for an AF Illumination Mission (GFT Setting Applied). ...................................................................................... F-13 Figure G-1. Laser Polar Target Location. ..............................................................................G-2 Figure G-2. Lase of Burst.......................................................................................................G-3 Figure G-3. Burst Spotting. ....................................................................................................G-3 Figure G-4. FFE Aimpoint. .....................................................................................................G-3 Figure G-5. Laser Polar Mission Processing. ........................................................................G-5 Figure G-6. Radar Spotting....................................................................................................G-5 Figure G-7. FFE Aimpoint. .....................................................................................................G-6 Figure G-8. Radar Mission Processing. .................................................................................G-7 Figure G-9. Cardinal Directions. ..........................................................................................G-12 Figure G-10. Ranging Rounds. ............................................................................................G-13 xvi TC 3-09.81 13 April 2016 Contents Figure G-11. Adjusting From Ranging Round. .................................................................... G-13 Figure G-12. Laser Polar Mission Processing..................................................................... G-16 Figure G-13. ROF (Laser Adjust-Fire Mission).................................................................... G-17 Figure G-14. Radar Mission Processing. ............................................................................ G-19 Figure G-15. Record of Fire (Radar Adjust-Fire Mission). .................................................. G-20 Figure G-16. Record of Fire (Destruction Mission).............................................................. G-22 Figure G-17. Record of Fire (Sweep and Zone Fire Mission). ............................................ G-25 Figure H-1 Decision Tree to Determine a Pasquill Weather Category.................................. H-3 Tables Table I-1. New or revised army terms ................................................................................... xxvi Table 3-1. Categories of Targets.......................................................................................... 3-22 Table 3-2. Guide for Cannon Attack of Typical Targets. ...................................................... 3-27 Table 3-3. Expected Area of Coverage (Meters).................................................................. 3-29 Table 3-4. Expected Percentage of Casualties or Personnel. ............................................. 3-30 Table 3-5. Improved Conventional Munitions....................................................................... 3-32 Table 4-1. Projectile Families, Propellant Types, and Charge Groups. ................................. 4-4 Table 4-2. Steps for Completing DA Form 4982-1............................................................. 4-14 Table 4-3. Example Determining ½◙ Correcting for Fuze.................................................... 4-16 Table 4-4. Completing DA Form 4982 for a First-Lot Calibration......................................... 4-17 Table 4-5. Completing DA Form 4982 for Subsequent Lot Calibration................................ 4-18 Table 4-6. Determination of Shooting Strength. ................................................................... 4-21 Table 4-7. Determining Unit PE After a Calibration.............................................................. 4-26 Table 5-1. Battery or Platoon Fire Order. ............................................................................... 5-5 Table 5-2. Fire Commands Sequence. ................................................................................ 5-18 Table 5-3. Battery or Platoon Fire Commands..................................................................... 5-19 Table 5-4. Other Fire Commands......................................................................................... 5-23 Table 6-1. Selection of LLHC and Azimuth of Lay. ................................................................ 6-8 Table 6-2. Firing Chart Preparation. ....................................................................................... 6-8 Table 6-3. Four-Step Plotting Method. ................................................................................... 6-9 Table 6-4. Constructing a Tick Mark (3-5-7 Method). .......................................................... 6-11 Table 6-5. Constructing North Indexes................................................................................. 6-14 Table 6-6. Constructing Azimuth Indexes. ........................................................................... 6-17 Table 6-7. Constructing Deflection Indexes. ........................................................................ 6-20 Table 6-8. Grid Coordinate Method (Four-Step Plotting Method). ....................................... 6-24 Table 6-9. Polar Plot Method of Target Location. .......................................................... 6-25 Table 6-10. Shift from a Known Point Method of Target Location. ...................................... 6-26 Table 6-11. Determining and Announcing Chart Data. ........................................................ 6-28 Table 6-12. Constructing an Observed Firing Chart............................................................. 6-32 Table 6-13. Computing Site by Using an Estimated VI. ....................................................... 6-36 13 April 2016 TC 3-09.81 xvii Contents Table 6-14. Computing an XO’s HB Registration. ............................................................... 6-38 Table 6-15. Procedure for GOT MINUS ASKED FOR Rule. ............................................... 6-40 Table 6-16. Construction of an Observed Firing Chart. ....................................................... 6-41 Table 6-17. Construction of an Observed Firing Chart, Position Area Survey Only............ 6-46 Table 8-1. Determination of Site without a GST. ................................................................... 8-3 Table 8-2. Determination of Vertical Angle. ........................................................................... 8-5 Table 8-3. Determination of Angle of Site and VA Using the GST. ....................................... 8-8 Table 8-4. Determination of Site Using the GST. .................................................................. 8-8 Table 8-5. Determination of High-Angle Site Using the 10-Mil Site Factor.......................... 8-10 Table 8-6. Determination of High-Angle Site with the TFT. ................................................. 8-10 Table 8-7. Sample Manual Computation of Site. ................................................................. 8-11 Table 8-8. Sample Manual Computation of VA. .................................................................. 8-12 Table 8-9. Sample Determination of Angle of Site and VA Using the GST. ........................ 8-12 Table 8-10. Sample Determination of Site Using the GST. ................................................. 8-13 Table 8-11. Sample Determination of High-Angle Site Using the 10-Mil Site Factor. ......... 8-14 Table 9-1. Mission Processing. .............................................................................................. 9-2 Table 9-2. Call for Fire Block Items........................................................................................ 9-6 Table 9-3. Upper Computational Space and Related Data Blocks Items.............................. 9-7 Table 9-4. Fire Order and Initial Fire Commands Block Items............................................... 9-8 Table 9-5. Message to Observer Block Items........................................................................ 9-9 Table 9-6. Fire Planning and Observer Subsequent Corrections Block Items. ................... 9-10 Table 9-7. Subsequent Fire Commands Block Item. ........................................................... 9-10 Table 9-8. Lower Computational Space and Administrative Blocks Items. ......................... 9-11 Table 9-9. Computation of Data Without a GFT Setting. ..................................................... 9-12 Table 9-10. HE/Q Adjust-Fire Mission. ................................................................................ 9-14 Table 9-11. Police of the Record of Fire. ............................................................................. 9-15 Table 9-12. Subsequent Adjustment of an HE/Q Fire Mission. ........................................... 9-16 Table 9-13. HE/TI Fire Mission with HE/Q in Adjustment. ................................................... 9-19 Table 9-14. Adjustment of Time Fuze.................................................................................. 9-20 Table 9-15. HE/TI FFE Fire Mission Process. ..................................................................... 9-22 Table 9-16. HE/VT Fire Mission with HE/Q in Adjustment Process. ................................... 9-25 Table 9-17. HE/VT FFE Fire Mission Process. .................................................................... 9-27 Table 9-18. WP/Q FFE Mission Following HE Adjustment Process.................................... 9-29 Table 9-19. HE High-Angle Adjust-Fire Mission. ................................................................. 9-34 Table 9-20. High-Angle Subsequent Adjustment................................................................. 9-35 Table 9-21. One-Gun Illumination Fire Mission Process. .................................................... 9-39 Table 9-22. Illumination Subsequent Adjustment. ............................................................... 9-40 Table 9-23. Two-Gun Illumination Pattern Fire Mission Process......................................... 9-42 Table 9-24. Determination of the Firing Interval. ................................................................. 9-47 Table 9-25. High Angle Illumination Process. ...................................................................... 9-50 Table 10-1. Assurance of Registration Validity. ................................................................... 10-4 xviii TC 3-09.81 13 April 2016 Contents Table 10-2. Determine Adjusted Fuze Setting (Second Lot)................................................ 10-8 Table 10-3. Impact Phase of Precision Registration Example. ............................................ 10-8 Table 10-4. Time Phase of Precision Registration. ............................................................ 10-10 Table 10-5. HB/MPI Registration........................................................................................ 10-20 Table 10-6. Average Observer Readings. .......................................................................... 10-24 Table 10-7. Determining the MBL. ..................................................................................... 10-25 Table 10-8. Determination of the MBL. .............................................................................. 10-28 Table 10-9. Determination of the GFT Setting. .................................................................. 10-31 Table 10-10. Effect of Complementary Angle of Site. ........................................................ 10-32 Table 10-11. Determination of True Site and True Adjusted Elevation.............................. 10-39 Table 10-12. Total Range Correction. ................................................................................ 10-43 Table 10-13. Total Registration Corrections....................................................................... 10-45 Table 10-14. GFT Setting—Registering Piece is not BP. .................................................. 10-46 Table 10-15. Construction of a GFT Setting....................................................................... 10-47 Table 10-16. Construction of a Two-Plot or Multi-plot GFT Setting. .................................. 10-49 Table 10-17. Construct GFT Setting on Illuminating GFT (HE Registration). .................... 10-50 Table 10-18. Update of a GFT When Transferring From Map Spot or Observed Firing Chart. .............................................................................................................. 10-50 Table 10-19. High-Angle Transfer Limits............................................................................ 10-53 Table 10-20. GFT Setting for Non-registering Unit. ........................................................... 10-54 Table 11-1. Five Steps to Improve Firing Data..................................................................... 11-2 Table 11-2. Concurrent Met Technique (Vowel Rule). ....................................................... 11-14 Table 11-3. Concurrent Met Technique (RATT Rule). ....................................................... 11-16 Table 11-4. Solution of a Concurrent Met. ......................................................................... 11-16 Table 11-5. Solution of a Met to Met Check Gauge Point.................................................. 11-41 Table 12-1. Plot Howitzer Location for Weapons with the M100-Series Sight................... 12-10 Table 12-2. Example of Howitzer Displacement. ............................................................... 12-11 Table 12-3. Plot Howitzer Location for Weapons with the M100-Series Sight................... 12-14 Table 12-4. Determination of Base Piece Grid................................................................... 12-16 Table 12-5. Determination of TGPCs. ................................................................................ 12-18 Table 12-6. Determination of TGPCs for all sheafs. .......................................................... 12-20 Table 12-7. Determination of Hasty TGPCs....................................................................... 12-22 Table 12-8. Completion of DA Form 4757.......................................................................... 12-23 Table 12-9. Computation of Special Corrections................................................................ 12-26 Table 12-10. Processing Fire Missions with the M17......................................................... 12-30 Table 12-11. Determination of Subsequent Corrections for a Laser Adjust-Fire Mission. ........................................................................................................... 12-31 Table 13-1. Determining Firing Data for a RAP Fire Mission. .............................................. 13-1 Table 13-2. Quick Smoke Technique. .................................................................................. 13-8 Table 13-3. Shell Separation and Upwind Offset for Smoke Munitions. ............................ 13-14 Table 13-4. M825 Smoke Technique. ................................................................................ 13-15 Table 13-5. Methods for Determining DPICM Firing Data. ................................................ 13-20 13 April 2016 TC 3-09.81 xix Contents Table 13-6. Mine Employment Matrix. ............................................................................... 13-26 Table 13-7. Mine Employment Table Number 1. ............................................................... 13-27 Table 13-8. Mine Employment Table Number 2. ............................................................... 13-27 Table 13-9. Mine Employment Table Number 3. ............................................................... 13-28 Table 13-10. Mine Employment Table Number 4. ............................................................. 13-28 Table 13-11. Mine Employment Table Number 5. ............................................................. 13-28 Table 13-12. Mine Employment Table Number 6. ............................................................. 13-29 Table 13-13. Mine Employment Table Number 7. ............................................................. 13-29 Table 13-14. Mine Employment Table Number 8. ............................................................. 13-29 Table 13-15. Desired Density Rounds per Aimpoint.......................................................... 13-31 Table 13-16. Recommended Minefield Density for Shell RAAMS..................................... 13-31 Table 13-17. Recommended Minefield Density for Shell ADAM. ...................................... 13-31 Table 13-18. Block-by-Block Explanation of DA Form 5032.............................................. 13-40 Table 13-19. Use of Safety Zone Tables. .......................................................................... 13-43 Table 13-20. RAAMS – Low Angle. ................................................................................... 13-43 Table 13-21. ADAM – Low Angle....................................................................................... 13-43 Table 13-22. RAAMS and ADAM – High Angle. ................................................................ 13-43 Table 13-23. Shell ADAM Employment Procedures. ......................................................... 13-44 Table 13-24. Shell RAAMS Employment Procedures. ...................................................... 13-46 Table 14-1. Emergency Firing Chart Procedures. ............................................................... 14-2 Table 14-2. M19 or M17 Plotting Board Procedures. .......................................................... 14-9 Table 14-3. Emergency Fire Mission. ................................................................................ 14-10 Table 15-1. Four Basic Steps of Manual Safety Production. ............................................... 15-5 Table 15-2. Construction of a Basic Safety Diagram........................................................... 15-7 Table 15-3. Low Angle Procedures...................................................................................... 15-9 Table 15-4. Tables and Addendums Required for Safety Computations. ......................... 15-13 Table 15-5. Determination for Updating Safety Based on Updated Non-Standard Conditions....................................................................................................... 15-15 Table 15-6. Procedures to Determine Maximum Effective Illumination Area. ................... 15-22 Table 15-7. High Angle Procedures................................................................................... 15-23 Table 15-8. Manual Minimum QE Computations. .............................................................. 15-32 Table 15-9. RFT Example for Howitzer Platoon. ............................................................... 15-32 Table 15-10. Manual Armed VT Minimum QE Computations. .......................................... 15-33 Table 15-11. Intervening Crest, Option 1........................................................................... 15-34 Table A-1. Content of Fire Direction Set 3. ............................................................................ A-5 Table A-2. Content of Fire Direction Set 4. ............................................................................ A-5 Table A-3. Contents of Plotting Set........................................................................................ A-5 Table C-1. 105-mm Planning Ranges....................................................................................C-1 Table C-2. M109A6/M198 155-mm Planning Ranges. .......................................................... C-1 Table C-3. M777 155-mm Planning Ranges. ........................................................................ C-4 Table C-4. MLRS/HIMARS Planning Ranges........................................................................C-6 xx TC 3-09.81 13 April 2016 Contents Table D-1. Determining Replot Deflection. ........................................................................... D-3 Table D-2. Determining Replot Grid and Altitude by Successive Approximation................. D-3 Table D-3. Determining Replot Deflection Without Target Refinements.............................. D-6 Table D-4. Determining Replot Grid and Altitude Without Target Refinements................... D-6 Table D-5. Determining Replot Grid, Altitude, and Refinement Data (Time Fuze) with Target Refinements. .......................................................................................... D-7 Table E-1. Automated Mission Processing. ...........................................................................E-2 Table E-2. Establishing a Manual Backup..............................................................................E-5 Table E-3. Switching from Automated to Manual Mission Processing...................................E-7 Table E-4. Determining Range K. ..........................................................................................E-8 Table F-1. Determining Basic HE Data with the 155AM3 HE M107 GFT..............................F-1 Table F-2. Determine Basic HE Data with the 155AM3 HE M107 High Angle GFT. .............F-3 Table F-3. Determining M483A1or M825/A1 Data with the 155AM3 HE M107 GFT.............F-3 Table F-4. Determining ADAM and RAAMS Data With 155AN2 M483A1 GFT.....................F-4 Table F-5. Construct GFT Setting on Illuminating GFT (HE Registration).............................F-5 Table F-6. Determining Firing Data by Using an Illum GFT. ..................................................F-5 Table F-7. HE Adjust-Fire Mission with Fuze VT I/E. .............................................................F-6 Table F-8. HE Adjust-Fire Mission with Shell DPICM I/E. ......................................................F-8 Table F-9. HE High-Angle FFE Mission with Fuze VT Using the High-Angle GFT (GFT Setting Applied). ......................................................................................F-10 Table F-10. Illumination AF Mission Using the Illumination GFT (GFT Setting Applied). ............................................................................................................F-12 Table G-1. Computational Procedure for Observer-Adjusted FPF. ...................................... G-1 Table G-2. Procedures for Laser Adjust-Fire Mission. .......................................................... G-4 Table G-3. Determining Difference Between Grid Coordinates of Target Location and Burst Location. ................................................................................................... G-6 Table G-4. Sheaf Fronts. ....................................................................................................... G-8 Table G-5. Sheaf Depths....................................................................................................... G-9 Table G-6. Determining Combination of Sweep and Zone Fires. ....................................... G-10 Table G-7. Processing a Laser Adjust-Fire Mission. ........................................................... G-15 Table G-8. Processing a Radar Adjust-Fire Mission. .......................................................... G-18 Table G-9. Processing a Destruction Mission. .................................................................... G-21 Table G-10. Processing a Sweep and Zone Fire Mission. .................................................. G-23 Table H-1. Smoke Table........................................................................................................ H-2 Table H-2. Weather Type. ..................................................................................................... H-3 Table H-3. Mean Windspeed for Pasquill Category (WS)..................................................... H-4 Table H-4. M825 Munition Expenditure Table (Near Infrared, 80% Relative Humidity)........ H-5 Table H-5. M825 Munition Expenditure Table (Near Infrared, 50% Relative Humidity)........ H-6 Table H-6. M825 Munition Expenditure Table (Near Infrared, 20% Relative Humidity)........ H-7 Table H-7. M825 Munition Expenditure Table (Visible, 80% Relative Humidity). ................. H-8 Table H-8. M825 Munition Expenditure Table (Visible, 50% Relative Humidity). ................. H-9 Table H-9. M825 Munition Expenditure Table (Visible, 20% Relative Humidity). ............... H-10 13 April 2016 TC 3-09.81 xxi Contents Table H-10. M116 HC Munition Expenditure Table (Near Infrared, 80% Relative Humidity)........................................................................................................... H-11 Table H-11. M116 HC Munition Expenditure Table (Near Infrared, 50% Relative Humidity)........................................................................................................... H-12 Table H-12. M116 HC Munition Expenditure Table (Near Infrared, 20% Relative Humidity)........................................................................................................... H-13 Table H-13. M116 HC Munition Expenditure Table (Visible, 80% Relative Humidity). .......H-14 Table H-14. M116 HC Munition Expenditure Table (Visible, 50% Relative Humidity). .......H-15 Table H-15. M116 HC Munition Expenditure Table (Visible, 20% Relative Humidity). .......H-16 Table H-16. M84A1 HC Munition Expenditure Table (Visible, 80% Relative Humidity). .....H-17 Table H-17. M84A1 HC Munition Expenditure Table (Visible, 50% Relative Humidity). .....H-18 Table H-18. M84A1 HC Munition Expenditure Table (Visible, 20% Relative Humidity). .....H-19 Table H-19. M110 WP Munition Expenditure Table (Near Infrared, 80% Relative Humidity)........................................................................................................... H-20 Table H-20. M110 WP Munition Expenditure Table (Near Infrared, 50% Relative Humidity)........................................................................................................... H-21 Table H-21. M110 WP Munition Expenditure Table (Near Infrared, 20% Relative Humidity)........................................................................................................... H-22 Table H-22. M110 WP Munition Expenditure Table (Visible, 80% Relative Humidity). .......H-23 Table H-23. M110 WP Munition Expenditure Table (Visible, 50% Relative Humidity). .......H-24 Table H-24. M110 WP Munition Expenditure Table (Visible, 20% Relative Humidity). .......H-25 Table H-25. M60A2 WP Munition Expenditure Table (Visible, 80% Relative Humidity). ....H-26 Table H-26. M60A2 WP Munition Expenditure Table (Visible, 50% Relative Humidity). ....H-27 Table H-27. M60A2 WP Munition Expenditure Table (Visible, 20% Relative Humidity). ....H-28 xxii TC 3-09.81 13 April 2016 Preface Training Circular (TC) 3-09.81 sets forth the doctrine pertaining to the employment of artillery fires. It explains all aspects of the manual cannon gunnery problem and presents a practical application of the science of ballistics. It includes step-by-step instructions for manually solving the gunnery problem which can be applied within the framework of decisive action or unified land operations. It is applicable to any Army personnel at the battalion or battery responsible to delivered field artillery fires. The principal audience for ATP 3-09.42 is all members of the Profession of Arms. This includes field artillery Soldiers and combined arms chain of command field and company grade officers, middle-grade and senior noncommissioned officers (NCO), and battalion and squadron command groups and staffs. This manual also provides guidance for division and corps leaders and staffs in training for and employment of the BCT in decisive action. This publication may also be used by other Army organizations to assist in their planning for support of battalions. This manual builds on the collective knowledge and experience gained through recent operations, numerous exercises, and the deliberate process of informed reasoning. It is rooted in time-tested principles and fundamentals, while accommodating new technologies and diverse threats to national security. Commanders, staffs, and subordinates ensure their decisions and actions comply with applicable United States, international, and, in some cases, host-nation laws and regulations. Commanders at all levels ensure that their Soldiers operate in accordance with the law of war and the rules of engagement. (See FM 27-10.) TC 3-09.81 uses joint terms where applicable. Selected joint and Army terms and definitions appear in both the glossary and the text. Terms for which publication TC 3-09.81 is the proponent publication (the authority) are marked with an asterisk (*) in the glossary. Definitions for which Publication TC 3-09.81 is the proponent publication are boldfaced in the text with the term being italicized. For other definitions shown in the text, the term is italicized and the number of the proponent publication follows the definition. TC 3-09.81 applies to the Active Army, Army National Guard/Army National Guard of the United States, and United States Army Reserve unless otherwise stated. The proponent for TC 3-09.81 is the United States Army Fires Center of Excellence. The preparing agency is the U.S. Army Fires Center of Excellence, Directorate of Training and Doctrine. Send comments and recommendations on Department of the Army (DA) Form 2028, Recommended Changes to Publications and Blank Forms, to Directorate of Training and Doctrine, 700 McNair Avenue, Suite 128, ATTN: ATSF-DD (TC 309.81), Fort Sill, OK 73503-4436; by email to: usarmy.sill.fcoe.mbx.dotd-doctrine-inbox@mail.mil. 13 April 2016 TC 3-09.81 xxiii This page intentionally left blank. Introduction Army and Marine Corps forces are employed to deliver fires in support of the maneuver commander. Consequently, this TC is grounded in Army and Marine Corps doctrine publications such as Army Doctrine Publication (ADP), Army Doctrine Reference Publication (ADRP) 3-09 to field artillery operations techniques in support of the maneuver commander, Marine Corps Warfighting Publication (MCWP) 316.1. Artillery Operations and Marine Corps Interim Publication (MCIP) 3-16.01. Tactics, Techniques, and Procedures for Lightweight 155mm. Techniques are non-prescriptive ways or methods used to perform missions, functions, or tasks. The techniques herein build on the collective knowledge and experience gained through recent operations, numerous exercises, and the deliberate process of informed reasoning. These techniques are rooted in the deliver manual gunnery principles identified in TC 3-09.81, and accommodate force design changes, new technologies and diverse threats. TC 3-09.81 is organized into 15 chapters and supporting appendixes A through H. Chapter 1 is an introduction to the gunnery problem and the relationship between the gunnery team for the effective accomplishment of tasks during operations. Chapter 2 describes the responsibilities of members of the fire direction center (FDC), and the battery organization in the brigade combat team (BCT). Chapter 3 describes a practical application of the science of ballistics. Chapter 4 describes the requirements muzzle velocity management and guidance in establishing an order of preference when managing muzzle velocity. Chapter 5 details the procedures for determine fire order, message to observer, and fire commands. Chapter 6 describes one of the elements to the solution of the gunnery problem by determination of chart data. Chapter 7 described the use of tabular firing tables (TFT) and graphical firing tables (GFT) in the solution of the gunnery problem. Chapter 8 discuses the procedures that are follow to account for the difference in altitude between the firing unit and the target. Chapter 9 details the use of the record of fire as well as the basic mission processing for high explosive and illumination munitions. Chapter 10 describes the means of determining cumulative errors and the correction for those errors. It explains registrations and their application to the gunnery problem. Chapter 11 describes the met techniques that allow a unit to account for the effects of non standard conditions and achieve first round fire for effect. Chapter 12 explains the techniques that can be use on the battlefield to enhance survivability. Chapter 13 discusses the characteristics and procedures or techniques required to fire special munitions. Chapter 14 provides guidance on delivering of fire under emergency situations. Chapter 15 provides guidance on the determination of safety and executive officer minimum quadrant elevation. Appendix A provides a standard operation procedure that can be use a guideline for setting the fire direction center. 13 April 2016 TC 3-09.81 xxv Introduction Appendix B describes the procedures that can be follow when a unit does not achieve accurate first round and is in needs of troubleshoot. Appendix C provides planning ranges for artillery weapons systems. Appendix D described the procedures to determine the refinements data transmitted by the observer. Appendix E describes the basic operation of an automated fire direction center. Appendix F assists in the determination of firing data with a graphical firing table. Appendix G is a supplement of chapter 13 which details more common special situations. Appendix H contains the tables for firing smoke missions. Based on current doctrinal changes, certain terms have been added, modified, or rescinded for purposes of this manual. The glossary contains acronyms and defined terms. Table I-1. New or revised army terms Term vertical angle Remarks Modified the definition and changed the proponent manual from ATP 3-09.30 to TC 3-09.81. xxvi TC 3-09.81 13 April 2016 Chapter 1 The Gunnery Problem and the Gunnery Team The mission of the Field Artillery is to destroy, defeat or disrupt the enemy with integrated fires to enable maneuver commanders to dominate in unified land operations (ADRP 3-09). The mission of the Firing Battery is to destroy, neutralize, or suppress the enemy by indirect cannon, mortars, rocket, and missile fires and to help integrate all fire support assets into combined arms operations. Field artillery weapons are normally employed in masked or defilade positions to conceal them from the enemy. Placing the firing platoon in defilade precludes direct fire on most targets. Consequently, indirect fire must be used when Field Artillery (FA) weapons fire on targets that are not visible from the weapons. Indirect fire is 1. Fire delivered at a target not visible to the firing unit. 2. Fire delivered to a target that is not itself used as a point of aim for the weapons or the director. The gunnery problem is an indirect fire problem. Solving the problem requires weapon and ammunition settings that, when applied to the weapon and ammunition, will cause the projectile to achieve the desired effects on the target. GUNNERY PROBLEM SOLUTION 1-1. The steps in solving the gunnery problem are as follows:  Determine the location of the target and know the location of the firing unit.  Determine chart (map) data (deflection, range from the weapons to the target).  Determine altitude of the target, vertical interval (VI) and site (SI).  Compensate for nonstandard conditions (meteorological corrections using concurrent and subsequent met technique applications).  Convert chart data to firing data (shell, charge, fuze, fuze setting, deflection, and quadrant elevation).  Apply the firing data to the weapon and ammunition. 1-2. The solution to the problem provides weapon and ammunition settings that will cause the projectile to function on or at the predetermined height above the target. This is necessary so the desired effects will be achieved. FIELD ARTILLERY GUNNERY TEAM 1-3. The coordinated efforts of the field artillery gunnery team are required to accomplish the solution of the gunnery problem outlined in paragraph 1-1. The elements for the team must be linked by an adequate communications system. Note: The terms battery and platoon used throughout this manual are synonymous, unless otherwise stated. 1-4. Observer. The observer and/or the target acquisition assets serve as the “eyes and ears” of all indirect fire systems. The role of the forward observer is to detect and locate suitable indirect fire targets within his zone of observation and bring fires on them. When a target is to be attacked, the observer 13 April 2016 TC 3-09.81 1-1 Chapter 1 transmits a call for fire and adjusts the fires onto the target as necessary. A call for fire is a request for fire containing data necessary for obtaining the required fire on a target. An observer provides surveillance data of his own fires and any other fires in his zone of observation. Trained and untrained observers include:  Forward Observers (FOs).  Fire support teams (FISTs).  Air and naval gunfire liaison company (ANGLICO).  Firepower control teams (FCTs).  Any other friendly battlefield personnel. 1-5. Target Acquisition. Target acquisition (TA) assets also function as observers. They provide accurate and timely detection, identification, and location of ground targets, collect combat and/or target information, orient and/or cue intelligence sources, and permit immediate attack of specific targets. Field artillery TA assets include the following:  Weapons-locating radar sections.  Aircraft radar systems. Note. See Army Techniques Publication (ATP) 3-09.12 for a discussion of TA assets. 1-6. Fire Direction and the Fire Direction Center. Fire direction is 1. The tactical employment of firepower exercising the tactical command of one or more units in the selection of targets, the concentration and distribution of fire, and the allocation of ammunition for each mission. 2. The methods and techniques used to convert target information into the appropriate fire commands. The fire direction center serves as the “brains” of the gunnery team. It is the control center for the gunnery team and is part of the firing battery headquarters. The FDC personnel receive calls for fire directly from an observer or they may be relayed through the battalion FDC. The FDC will then process that information by using tactical and technical fire direction procedures.  Tactical Fire Direction includes processing calls for fire and determining the appropriate method of fire, ammunition expenditure, unit(s) to fire, and time of attack. The fire direction officer’s (FDO) decision on how to engage the target is concisely stated as a FIRE ORDER.  Technical Fire Direction is the process of converting weapon and ammunition characteristics (muzzle velocity, propellant temperature, and projectile weight), weapon and target locations, and met information into firing data. Firing data consist of shell charge, fuze, fuze setting, deflection, and quadrant elevation. The FDC transmits firing data to the guns as FIRE COMMANDS. 1-7. Firing Battery. The firing battery serves as the “muscle” of the gunnery team. The firing battery includes the battery headquarters (HQ), the howitzer sections, the ammunition section and the FDC. The howitzer sections apply the technical firing data to the weapon and the ammunition. Note: See ATP 3-09.50 for organization and employment considerations of the firing sections. FIVE REQUIREMENTS FOR ACCURATE FIRE 1-8. The goal of the firing battery is to achieve accurate first-round fire for effect (FFE) on a target. Fire for effect is 1. A command to indicate that fire for effect is desired. 2. Fire that is intended to achieve the desired result on target. In order to accomplish this goal an artillery unit must compensate for nonstandard conditions as completely as time and the tactical situation permit. There are five requirements for achieving accurate first-round fire for effect. These requirements are accurate target location and size, accurate firing unit location, accurate weapon and ammunition information, accurate meteorological information, and accurate computational procedures. If these requirements are met, the firing unit will be able to deliver accurate and timely fires in support of the ground-gaining arms. If the requirements for accurate fire cannot be met completely, the firing unit may be required to use adjust-fire (AF) missions to 1-2 TC 3-09.81 13 April 2016 The Gunnery Problem and the Gunnery Team engage targets. Adjust-fire missions can result in reduced effect on the target, increased ammunition expenditure, and greater possibility that the firing unit will be detected by hostile TA assets.  Accurate Target Location and Size. Establishing the range (RG) from the weapons to the target requires accurate and timely detection, identification, and location of ground targets. Determining their size and disposition on the ground is also necessary so that accurate firing data can be computed. Determining the appropriate time and type of attack requires that the target size (radius or other dimensions) and the direction and speed of movement are considered. Target location is determined by using the TA assets mentioned in paragraph 1-4 and 1-5.  Accurate Firing Unit Location. Accurate range and deflection from the firing unit to the target requires accurate weapon locations and that the FDC knows this location. The battalion survey section uses different equipments to provide accurate survey information for the battery location. Survey techniques available to the firing battery may also help in determining the location of each weapon. Note: These techniques are explained in ATP 3-09.50 and FM 6-2.  Accurate Weapon and Ammunition Information. The actual performance of the weapon is measured by the weapon muzzle velocity (velocity with which the projectile leaves the muzzle of the tube) for a projectile-propellant combination. The firing battery can measure the achieved muzzle velocity of a weapon and correct it for nonstandard projectile weight and propellant temperature; this is done through use of the Muzzle Velocity Systems (MVS). The corrections that the MVS makes are similar to those found in the Muzzle Velocity Correction Table (MVCT). Calibration should be conducted continuously by using the MVS. Firing tables and technical gunnery procedures allow the unit to consider specific ammunition information (projectile square weight, fuze type, and propellant temperature); thus, accurate firing data are possible.  Accurate Meteorological Information. The effects of weather on the projectile in flight must be considered, and firing data must compensate for those effects. Firing tables and technical gunnery procedures allow the unit to consider specific weather information (air temperature, air density/pressure, wind direction, and wind speed) in determining accurate firing data.  Accurate Computational Procedures. The computation of firing data must be accurate. Manual and automated techniques are designed to achieve accurate and timely delivery of fire. The balance between accuracy, speed, and the other requirements discussed in this chapter should be included in the computational procedures. Note: Nonstandard Conditions. If the five requirements for accurate fire cannot be met, the FDC needs to take steps to improve firing data (See Chapter 11). 13 April 2016 TC 3-09.81 1-3 This page intentionally left blank. Chapter 2 Firing Battery and Battery Organization The FA cannon battery is firing unit within the cannon battalion and is organized in one of two ways: a battery-based unit (3 x 6 organization) or a platoon-based unit (3 x 2 organization). In either case, they have the personnel and equipment needed to shoot, move, and communicate. This chapter describes the organization of the firing battery and the battery FDC. BATTERY ORGANIZATION IN THE BCT 2-1. The organization of all cannon batteries is basically the same. Differences in organization stem from differences in weapon caliber, whether the weapon is towed or self-propelled (SP), and whether the battery is in a Brigade Combat Team (BCT) or a Fires Brigade. The cannon battery is organized as follows: 2-2. Battery-based unit--consists of a battery headquarters and a firing battery.  The battery HQ has the personnel and equipment to perform mission command; supply; communications; and chemical, biological, radioactive, nuclear (CBRN) functions.  The firing battery has the personnel and equipment to determine firing data, fire the howitzers, and resupply ammunition. (In some units, ammunition assets may be consolidated at battalion level.) 2-3. Platoon-based unit--consists of a battery HQ and two firing platoons.  The battery HQ has the personnel and equipment to perform mission command, supply, communications, and chemical, biological, radioactive, nuclear (CBRN) functions.  Each firing platoon has the personnel and equipment to determine firing data, fire the howitzers, and resupply ammunition. (In some units, ammunition assets may be consolidated at battalion level.) BATTERY OR PLATOON FDC 2-4. The battery FDC performs the tactical and/or technical fire direction, while the battalion FDC performs tactical fire direction. If the FDC is operating without a battalion FDC, the battery FDC conducts both tactical and technical fire direction. The battery FDC receives the call for fire and converts the request into firing data. The firing data are then transmitted to the howitzer sections as fire commands. In addition to an FDC, United States Marine Corps (USMC) batteries have a battery operations center (BOC), which is organized and equipped to perform technical fire direction. BOCs enhance unit survivability, simplify displacements, and enable split-battery operations. In battery positions, BOC personnel may augment the FDC to facilitate 24-hour operations. 2-5. The FDC is organized to facilitate 24-hour operations Duties of manual FDC personnel follow. 2-6. Fire Direction Officer (FDO). The FDO is responsible for all FDC operations. He is responsible for the training of all FDC personnel, supervises the operation of the FDC, establishes standard operating procedure (SOP), checks target location, announces fire order, and ensures accuracy of firing data transmitted to the howitzers. USMC batteries also include an assistant executive officer (AXO). The AXO leads the BOC, assists the battery commander during displacement and stands duty in the FDC as the FDO to enable 24-hour operations. 2-7. Chief Fire Control Sergeant. The Chief Fire Control Sergeant is the technical expert and trainer in the FDC. He ensures that all equipment is on hand and operational, supervises computation of all data, ensures that all appropriate records are maintained, and helps the FDO as needed. He ensures smooth 13 April 2016 TC 3-09.81 2-1 Chapter 2 performance of the FDC in 24-hour operations and functions as the FDO in the FDO’s absence. The equivalent USMC billet description is Operations Chief. 2-8. Fire Direction Computer. The fire direction computer operates the primary means of computing firing data. He determines and announces fire commands. He also records mission-related data and other information as directed. The equivalent USMC billet description is Assistant Operations Chief (A-Ops Chief). There is an A-Ops Chief in both the FDC and the BOC. 2-9. Fire Direction Specialist. In a manual FDC, they serve alternately as Horizontal Control Operator (HCO), Vertical Control Operator (VCO) and Radiotelephone operator (RTO). The equivalent USMC billet description is Fire Control Man. These fire control men may perform the duties of the HCO, VCO, RTO, or driver as needed in either the FDC or BOC.  The HCO constructs and maintains the primary firing chart and determines and announces chart data. Chart data consist of: Chart Range, Chart Deflection and Angle T.  The VCO constructs the secondary firing chart checks chart data and determines and announces site.  The RTO or driver normally the operator of the FDC vehicle. He maintains the vehicle and the FDC-associated generators. In a manual FDC, he may also act as the recorder. 2-10. Fire direction is the employment of firepower. The objectives of fire direction are to provide continuous, accurate, and responsive fires under all conditions. Flexibility must be maintained to engage all types of targets over wide frontages, to mass the fires of all available units quickly, and to engage a number and variety of targets simultaneously. 2-11. The fire direction center is the element of the gunnery team with which the commander directs artillery firepower. The accuracy, flexibility, and speed in the execution of fire missions depend on:  Rapid and clear transmission of calls for fire.  Rapid and accurate computations.  Rapid and clear transmission of fire commands.  Integration of automated and manual equipment into an efficient, mutually supporting system.  Efficient use of communications equipment. RELATIONSHIP BETWEEN BATTERY OR PLATOON AND BATTALION FDC 2-12. There are two modes of operation under which fire direction can be conducted: battalion directed and autonomous. 2-13. Battalion Directed. In battalion-directed operations, calls for fire are transmitted from the observer to the battalion FDC. The battalion FDO is responsible for tactical fire direction. A fire order is transmitted to the firing units that are responsible for technical fire direction. The battalion FDC is responsible for relaying all fire mission related messages/reports to the observer. The firing units are responsible for transmitting all fire mission related messages to the battalion FDC. 2-14. Autonomous. In autonomous operations, calls for fire are transmitted from the observer to the firing unit FDC. The firing unit FDC is responsible for tactical and technical fire direction. The firing unit is responsible for transmitting all fire mission related messages/reports to the observer. The battalion FDC and the battalion fire support officer (FSO) monitor the calls for fire. The battalion FDC may take over control of the mission if the target warrants the massing of two or more batteries. The battalion FDC monitors the battery’s message to observer (MTO) to ensure that the battery has selected the appropriate ammunition and method of fire. The battalion FDC may change the battery’s plan of attack. If the target requires battalion fire, the firing unit FDO can request reinforcing fires from the battalion FDC. BATTALION FDC PERSONNEL 2-15. A battalion FDC is composed of a Fire Direction Officer, a Chief Fire Control Sergeant, a Fire Direction Computer, and Fire Direction Specialists. USMC battalion FDCs are composed of a Fire 2-2 TC 3-09.81 13 April 2016 Firing Battery and Battery Organization Direction Officer, Operations Chief, Operations Assistants, and Fire Control Men that facilitate 24-hour operations. The Operations Chief is the equivalent of the Chief Fire Control Sergeant, and the Operations Assistants are the equivalent of the Fire Direction Computer. The Fire Control Men may perform the duties of computer, HCO, VCO, RTO, or driver as needed. 2-16. Battalion Fire Direction Officer’s Duties. The FDO:  Is responsible for the overall organization and functioning of the battalion FDC.  Coordinates with the battalion operations staff officer (S-3) to ensure that all information regarding the tactical situation, unit mission, ammunition status, and commander’s guidance on the method of engagement of targets and control of ammunition expenditures is known and ensures that all information is passed to battery FDOs.  Ensures that all communications are properly established.  Coordinates with the Chief Fire Control Sergeant concerning data input, chart verification, transfer of registration corrections, average site or altitude, terrain gun position corrections (TGPCs) sectors, and any other special instructions.  Inspects target locations and monitors messages to observer when a mission is received by a battery FDC and intercedes when necessary.  Controls all battalion missions.  Supervises battalion muzzle velocity management. 2-17. Battalion Chief Fire Control Sergeant’s Duties. The Chief Fire Control Sergeant:  Serves as the battalion FDC’s technical expert (the actual supervisor and/or trainer of battalion FDC personnel) and assumes the duties of the battalion FDO in his absence.  Ensures that all battalion FDC equipment is operational and emplaced correctly.  Ensures coordination of all data throughout the battalion, to include current registration settings.  Ensures that the HCO’s chart include all pertinent known data.  Ensures that the situation map is properly posted, to include fire support coordination measures and the current tactical situation. 2-18. Battalion Fire Direction Computer’s Duties. The assistant chief computer:  Monitors all operations performed by the HCO.  Supervises maintenance and care of the generators.  Assumes the duties of the battalion Chief Fire Control Sergeant when he is absent.  Provide communications link with the battery FDCs.  Exchange information with the battery FDCs and pass battalion fire orders to the battery.  Record all data pertinent to fire missions that are transmitted to their battery.  Compute data for their battery when directed by the chief computer.  Use their fire direction net to communicate with the observer when battalion missions are conducted.  Assume the duties of the Fire Direction Computer when he is absent. 2-19. Horizontal Control Operator’s (HCO) Duties. The HCO:  Plots known data as directed by the assistant chief computer.  Determines target location, altitude and target segmentation as required.  Maintains equipment as required.  Plots the initial target location when a mission is received. 2-20. Radiotelephone Operator’s Duties. The RTO:  Establishes and maintains communications on the battalion’s command/fire direction (FD) net.  Determines and transmits the message to observer when battalion missions are conducted on the battalion counterfire (CF) net.  Encodes and decodes messages, target list, and fire plans.  Ensure proper authentication of appropriate messages and all fire missions. 13 April 2016 TC 3-09.81 2-3 Chapter 2  Records all traffic on applicable forms (i.e. DA Form 1594 Daily Staff Journal or Duty Officer's Log).  Maintains equipment as required. 2-4 TC 3-09.81 13 April 2016 Chapter 3 Ballistics Ballistics is the study of the firing, flight, and effect of ammunition. A fundamental understanding of ballistics is necessary to comprehend the factors that influence precision and accuracy and how to account for them in the determination of firing data. Gunnery is the practical application of ballistics so that the desired effects are obtained by fire. To ensure accurate fire, we must strive to account for and minimize those factors that cause round-to-round variations, particularly muzzle velocity. Ballistics can be broken down into four areas: interior, transitional, exterior, and terminal. Interior, transitional, and exterior ballistics directly affect the accuracy of artillery fire. SECTION I: INTERIOR BALLISTICS 3-1. Interior ballistics is the science that deals with the factors that affect the motion of the projectile within the tube. The total effect of all interior ballistic factors determines the velocity at which the projectile leaves the muzzle of the tube, which directly influences the range achieved by the projectile. This velocity, called muzzle velocity (MV), is expressed in meters per second to the nearest tenths (0.1 m/s). Actual measurements of the muzzle velocities of a sample of rounds corrected for the effects of nonstandard projectile weight and propellant temperature show the performance of a specific weapon for that projectile family-propellant lot-charge combination. The resulting measurement(s) are compared to the standard muzzle velocity shown in the firing table(s). This comparison gives the variation from standard, called muzzle velocity variation (MVV), for that weapon and projectile family-propellant lot-charge combination. Application of corrections to compensate for the effects of nonstandard muzzle velocity is an important element in computing accurate firing data. (For further discussion of muzzle velocity, see Chapter 4.) The following equation for muzzle velocity is valid for our purposes: MVV m/s = SHOOTING STRENGTH OF WPN + AMMUNITION EFFICIENCY 3-2. Tube wear, propellant efficiency, and projectile weight are the items normally accounted for in determination of a muzzle velocity. Other elements in the equation above generally have an effect not exceeding +/-1.5 m/s. As a matter of convenience, the other elements listed below are not individually measured, but their effects are realized to exist under the broader headings of shooting strength and ammunition efficiency. SHOOTING STRENGTH OF WEAPONS 1. Tube wear 2. Manufacturer tolerances 3. Reaction to recoil AMMUNITION EFFICIENCY 1. Propellant efficiency 2. Projectile efficiency a. Projectile weight (fuzed) b. Construction of (1) Rotating band or Obturating Band (2) Bourrelet 13 April 2016 TC 3-09.81 3-1 Chapter 3 NATURE OF PROPELLANT AND PROJECTILE MOVEMENT 3-3. A propellant is a low-order explosive that burns rather than detonates. In artillery weapons using separate-loading ammunition, the propellant burns within a chamber formed by the obturator spindle assembly, powder chamber, rotating band, and base of the projectile. For cannons using semi-fixed ammunition, the chamber is formed by the shell casing and the base of the projectile. When the propellant is ignited by the primer, the burning propellant generates gases. When these gases develop enough pressure to overcome initial bore resistance, the projectile begins its forward motion. PARTS OF THE CANNON TUBE THAT AFFECT INTERIOR BALLISTICS. 3-4. The breech recess receives the breechblock. The breech permits loading the howitzer from the rear. 3-5. The powder chamber receives the complete round of ammunition. It is the portion of the tube between the gas check seat and the centering slope (see figure 3-1 for illustration).  The gas check seat is the tapered surface in the rear interior of the tube on weapons firing separate-loading ammunition. It seats the split rings of the obturating mechanism when they expand under pressure in firing. This expansion creates a metal-to-metal seal and prevents the escape of gases through the rear or the breech. Weapons firing semi-fixed ammunition do not have gas check seats since the expansion of the case against the walls of the chamber provides a gas seal for-the breech.  The swiss groove is the cutaway portion of the powder chamber that allows the propellant to sit flush against the obturator spindle when the breech is closed. The swiss groove also holds the propellant in place at all angles of elevation.  The centering slope is the tapered portion at or near the forward end of the chamber that causes the projectile to center itself in the bore during loading. Figure 3-1. Cannon Tube. 3-6. The forcing cone is the tapered portion near the rear of the bore that allows the rotating band to be gradually engaged by the rifling, thereby centering the projectile in the bore. 3-2 TC 3-09.81 13 April 2016 Ballistics 3-7. The bore is the rifled portion of the tube (lands and grooves). It extends from the forcing cone to the muzzle. The rifled portion of the tube imparts spin to the projectile increasing stability in flight. The grooves are the depressions in the rifling. The lands are the raised portions. These parts engrave the rotating band. All United States (US) howitzers have a right-hand twist in rifling. 3-8. The bore evacuator is located on enclosed, self-propelled howitzers with semi-automatic breech mechanisms. It prevents contamination of the crew compartment by removing propellant gases from the bore after firing. The bore evacuator forces the gases to flow outward through the bore from a series of valves enclosed on the tube. 3-9. The caliber of a tube is the inside diameter of the tube as measured between opposite lands. 3-10. The counterbore is the portion at the front of the bore from which the lands have been removed to relieve stress and prevents the tube from cracking. 3-11. The muzzle brake is located at the end of the tube on some howitzers. As the projectile leaves the muzzle, the high-velocity gases strike the baffles of the muzzle brake and are deflected rearward and sideways. When striking the baffles, the gases exert a forward force on the baffles that partially counteracts and reduces the force of recoil. PARTS OF THE PROJECTILE TUBE THAT AFFECT INTERIOR BALLISTICS. 3-12. The projectile body has several components that affect ballistics. (See figure 3-2.) Two of these affect interior ballistics-the bourrelet and the rotating band or obturating band (found on certain projectiles). Figure 3-2. Separate Loading 155mm Projectile. 3-13. The bourrelet is the widest part of the projectile and is located immediately to the rear of the ogive. The bourrelet centers the forward part of the projectile in the tube and bears on the lands of the tube. When the projectile is fired, only the bourrelet and rotating band bear on the lands of the tube. 3-14. The rotating band is a band of soft metal (copper alloy) that is securely seated around the body of the projectile. When engaged with the forcing cones it provides forward obturation (the gas-tight seal 13 April 2016 TC 3-09.81 3-3 Chapter 3 required to develop pressure inside the tube). The rotating band prevents the escape of gas pressure from around the projectile. When the weapon is fired, the rotating band contacts the lands and grooves and is pressed between them. As the projectile travels the length of the cannon tube, over the lands and grooves, spin is imparted. The rifling for the entire length of the tube must be smooth and free of burrs and scars. This permits uniform seating of the projectile and gives a more uniform muzzle velocity. 3-15. The obturating band is a plastic band on certain projectiles. It provides forward obturation by preventing the escape of gas pressure from around the projectile. Note: The terms rotating band and obturating band used throughout this manual are synonymous, unless otherwise stated. THE SEQUENCE THAT OCCURS WITHIN THE CANNON TUBE 3-16. The projectile is rammed into the cannon tube and rests on the bourrelet. The rotating band contacts the lands and grooves at the forcing cone creating forward obturation. 3-17. The propellant is inserted into the powder chamber and the breech is closed. This provides rearward obturation. Note: For semi-fixed ammunition, the projectile and powder canister are inserted into the cannon tube and the breech is closed. The rotating band creates forward obturation while, upon firing, the rapid expansion of gases within the canister causes the canister to expand against the powder chamber walls creating rearward obturation. 3-18. The propellant explosive train is initiated by the ignition of the primer. The primer injects hot gases and incandescent particles into the igniter. The igniter burns and creates hot gases that flow between the powder grains and ignite the grains surfaces; the igniter and propellant combustion products then act together, perpetuating the flame spread until all the powder grains are ignited. 3-19. The chamber is sealed, in the rear by the breech and obturator spindle group (gas check seat) and forward by the rotating band of the projectile, so the gases and energy created by the primer, igniter, and propellant cannot escape. This results in a dramatic increase in the pressure and temperature within the chamber. The burning rate of the propellant is roughly proportional to the pressure, so the increase in pressure is accompanied by an increase in the rate at which further gas is produced. 3-20. The rising pressure is moderated by the motion of the projectile along the barrel. The pressure at which this motion begins is the shot-start pressure. The projectile will then almost immediately encounter the rifling, and the projectile will slow or stop again until the pressure has increased enough to overcome the resistance in the bore. The rotating band will be engraved to the shape of the rifling. The resistance decreases, thereby allowing the rapidly increasing pressure to accelerate the projectile. 3-21. As the projectile moves forward, it leaves behind an increasing volume to be filled by the highpressure propellant gases. The propellant is still burning, producing high-pressure gases so rapidly that the motion of the projectile cannot fully compensate. As a result, the pressure continues to rise until the peak pressure is reached. The peak pressure is attained when the projectile has traveled about one-tenth of the total length of a howitzer tube. 3-22. The rate at which extra space is being created behind the rapidly accelerating projectile then exceeds the rate at which high-pressure gas is being produced; thus the pressure begins to fall. The next stage is the all-burnt position at which the burning of the propellant is completed. However, there is still considerable pressure in the tube; therefore, for the remaining motion along the bore, the projectile continues to accelerate. As it approaches the muzzle, propellant gases expand, pressure falls, and acceleration lessens. At the moment the projectile leaves the howitzer, the pressure will have been reduced to about one-sixth of the peak pressure. Only about one-third of the energy developed pushes the projectile. The other two-thirds are absorbed by the recoiling parts or lost because of heat and metal expansion. 3-23. The flow of gases following the projectile out of the muzzle provides additional acceleration for a short distance (transitional ballistics); so that the full muzzle velocity is not reached until the projectile is 3-4 TC 3-09.81 13 April 2016 Ballistics some distance beyond the muzzle. The noise and shock of firing are caused by the jet action of the projectile as it escapes the flow of gases and encounters the atmosphere. After this, the projectile breaks away from the influence of the gun and begins independent flight. 3-24. This entire sequence, from primer firing to muzzle exit, typically occurs within 15 milliseconds but perhaps as much as 25 milliseconds for a large artillery howitzer. PRESSURE TRAVEL CURVES 3-25. Once the propellant ignites, gases are generated that develop enough pressure to overcome initial bore resistance, thereby moving the projectile. Two opposing forces act on a projectile within the howitzer. The first is a propelling force caused by the high-pressure propellant gases pushing on the base of the projectile. The second is a frictional force between the projectile and bore, which includes the high resistance during the engraving process that opposes the motion of the projectile. The peak pressure, together with the travel of the projectile in the bore (pressure travel curve), determines the velocity at which the projectile leaves the tube. 3-26. To analyze the desired development of pressure within the tube, we identify three types of pressure travel curves:  An elastic strength pressure travel curve represents the greatest interior pressure that the construction of the tube (thickness of the wall of the powder chamber, thickness of the tube, composition of the tube or chamber, and so on) will allow. It decreases as the projectile travels toward the muzzle because the thickness of the tube decreases.  A permissible pressure travel curve mirrors the elastic strength pressure travel curve and accounts for a certain factor of safety. It also decreases as the projectile travels through the tube because tube thickness decreases.  An actual pressure travel curve represents the actual pressure developed during firing within the tube. Initially, pressure increases dramatically as the repelling charge explosive train initiated and the initial resistance of the rammed projectile is overcome. After that resistance is overcome, the actual pressure gradually decreases because of the concepts explained by Boyle’s Law. The actual pressure should never exceed the permissible pressure. 3-27. Initial Excessive Pressure. This is undesirable pressure travel curve. It exceeds the elastic strength pressure and permissible pressure. Causes of this travel curve would be an obstruction in the tube, a dirty tube, an “extra” propellant placed in the chamber, an un-fuzed projectile, or a cracked projectile. See figure 3-3. Figure 3-3. Initial Excessive Pressure. 3-28. Delayed Excessive Pressure. This is an undesirable pressure travel curve. It exceeds the elastic strength pressure and permissible pressure. Causes that would result in this travel curve would be using wet powder or powder reversed. See figure 3-4 on page 3-6. 13 April 2016 TC 3-09.81 3-5 Chapter 3 Figure 3-4. Delayed Excessive Pressure. 3-29. Desirable Pressure Travel Curve. This curve does not exceed permissible pressure. It develops peak pressure at about one-tenth the length of the tube. See figure 3-5. Figure 3-5. Desirable Pressure Travel Curve. FACTORS THAT AFFECT THE VELOCITY PERFORMANCE OF A WEAPON PROJECTILE FAMILYPROPELLANT LOT-CHARGE COMBINATION: 3-30. An increase in the rate of propellant burning increases the resulting gas pressure developed within the chamber. An example of this is the performance of the multi-perforated propellant grains used in M232A1 Modular Artillery Charge System (MACS). The result is that the propellant burns at a faster rate, more gases are produced, gas pressure is increased, and the projectile develops a greater muzzle velocity. Damage to powder grains, such as cracking and splitting from improper handling, or slight differences in the manufacturing process between different lots of the same propellant type also affect the rate of burn and thus the muzzle velocity. 3-31. An increase in the size of the chamber without a corresponding increase in the amount of propellant decreases gas pressure; as a result, muzzle velocity will be less. 3-32. Gas escaping around the projectile decreases chamber pressure. 3-33. An increase in bore resistance to projectile movement before peak pressure increases the pressure developed within the tube. Generally, this results in a dragging effect on the projectile, with a corresponding decrease in the developed muzzle velocity. Temporary variations in bore resistance can be caused by excessive deposits of residue within the cannon tube and on projectiles and by temperature differences between the inner and outer surfaces of the cannon tube. FACTORS CAUSING NONSTANDARD VELOCITIES. 3-34. Nonstandard muzzle velocity is expressed as a variation (plus or minus so many meters per second) from the accepted standard. Round-to-round corrections for dispersion cannot be made. Each of the following factors that cause nonstandard conditions is treated as a single entity assuming no influence from 3-6 TC 3-09.81 13 April 2016 Ballistics related factors applicable firing tables list the standard value of muzzle velocity for each charge. These standard values are based on an assumed set of standard conditions. These values are points of departure and not absolute standards. Essentially, we cannot assume that a given weapon projectile family-propellant type-charge combination when fired will produce the standard muzzle velocity. See figure 3-6 for a graph of velocity changes by round. Figure 3-6. Velocity Changes. 3-35. Velocity trends. Not all rounds of a series fired from the same weapon and using the same ammunition lot will develop the same muzzle velocity. Under most conditions, the first few rounds follow a somewhat regular pattern rather than the random pattern associated with normal dispersion. This phenomenon is called velocity trends (or velocity dispersion), and the magnitude varies with the cannon, charge, and tube condition at the time each round is fired. Velocity trends cannot be accurately predicted; thus, any attempt to correct for the effects of velocity trends is impractical. Generally, the magnitude and duration of velocity trends can be minimized when firing is started with a tube that is clean and completely free of oil. (See figure 3-6.) 3-36. Ammunition lots. Each ammunition, projectile, and propellant lot has its own mean performance level in relation to a common weapon. Although the round-to-round variations within a given lot of the same ammunition types are similar, the mean velocity developed by one lot may differ significantly in comparison to that of another lot. With separate-loading ammunition, both the projectile and propellant lots must be identified. Projectile lots allow for rapid identification of weight differences. Although other projectile factors affect achieved muzzle velocity (such as, diameter and hardness of rotating band), the cumulative effect of these elements generally does not exceed +/- 1.5 m/s. As a matter of convenience and speed, they are ignored in the computation of firing data. 3-37. Tolerances in new weapons. All new cannons of a given caliber and model will not necessarily develop the same muzzle velocity. In a new tube, the mean factors affecting muzzle velocity are variations in the size of the powder chamber and the interior dimensions of the bore. If a battalion equipped with new cannons fired all of them with a common lot of ammunition, a variation of +/-4 m/s between the cannon developing the greatest muzzle velocity and the cannon developing the lowest muzzle velocity would not be unusual. Calibration of all cannons allows the firing unit to compensate for small variations in the 13 April 2016 TC 3-09.81 3-7 Chapter 3 manufacture of cannon tubes and the resulting variation in developed muzzle velocity. The MVV caused by inconsistencies in tube manufacture remains constant and is valid for the life of the tube. 3-38. Tube wear. Continued firing of a cannon wears away portions of the bore by the actions of hot gases and chemicals and movement of the projectile within the tube. These erosive actions are more pronounced when higher charges are fired. The greater the tube wear, the more the muzzle velocity decreases. Normal wear can be minimized by careful selection of the charge and by proper cleaning of both the tube and the ammunition. 3-39. Non-uniform ramming. Weak, non-uniform ramming results in an unnecessary and preventable increase in the size of the dispersion pattern. Weak ramming decreases the volume of the chamber and thereby theoretically increases the pressure imparted to the projectile. This occurs because the pressure of a gas varies inversely with volume. Therefore, only a partial gain in muzzle velocity might be achieved. Of greater note is the improper seating of the projectile within the tube. Improper seating can allow some of the expanding gases to escape around the rotating band of the projectile and thus result in decreased muzzle velocity. The combined effects of a smaller chamber and escaping gases are difficult to predict. Hard, uniform ramming is desired for all rounds. When semi-fixed ammunition is fired, the principles of varying the size of the chamber and escape of gases still apply, particularly when ammunition is fired through worn tubes. When firing semi-fixed ammunition, rearward obturation is obtained by the expansion of the cartridge case against the walls of the powder chamber. Proper seating of the cartridge case is important in reducing the escape of gases. 3-40. Rotating bands. The ideal rotating band permits proper seating of the projectile within the cannon tube. Proper seating of the projectile allows forward obturation, uniform pressure buildup, and initial resistance to projectile movement within the tube. The rotating band is also designed to provide a minimum drag effect on the projectile once the projectile overcomes the resistance to movement and starts to move. Dirt or burrs on the rotating band may cause improper seating. This increases tube wear and contributes to velocity dispersion. If excessively worn, the lands may not engage the rotating band well enough to impart the proper spin to the projectile. Insufficient spin reduces projectile stability in flight and can result in dangerously erratic round performance. When erratic rounds occur or excessive tube wear is noted, ordnance teams should be requested to determine the serviceability of the tube. 3-41. Propellant and projectile temperatures. Any combustible material burns more rapidly when heated before ignition. When a propellant burns more rapidly than would be expected under standard conditions, gases are produced more rapidly and the pressure imparted to the projectile is greater. As a result, the muzzle velocity will be greater than standard and the projectile will travel farther. Table E in the tabular firing tables lists the magnitude of change in muzzle velocity resulting from a propellant temperature that is greater or less than standard. Appropriate corrections can be extracted from that table; however, such corrections are valid only if they are determined relative to the true propellant temperature. The temperature of propellant in sealed containers remains fairly uniform though not necessarily at the standard propellant temperature (70 degrees Fahrenheit). Once propellant has been unpacked, its temperature more rapidly approaches the air temperature. The time and type of exposure to the weather result in temperature variations from round to round and within the firing unit. It is currently impractical to measure propellant temperature and apply corrections for each round fired by each cannon. Positive action must be taken to maintain uniform projectile and propellant temperatures in the form of proper ammunition storage and handling procedures. Failure to do this results in erratic firing. The effect of an extreme change in projectile or propellant temperature can invalidate even the most recent corrections determined from a registration.  Ready ammunition should be kept off the ground and protected from dirt, moisture, and direct sunlight. At least 6 inches of airspace between the ammunition and protective covering on the sides, 6 inches of dunnage on the bottom, and the roof 18 inches from the top of the stack. These precautions will allow propellant and projectile temperatures to approach the air temperature at a uniform rate throughout the firing unit.  Propellant should be prepared in advance so that it is never necessary to fire freshly unpacked ammunition with ammunition that has been exposed to weather during a fire mission.  Ammunition should be fired in the order in which it was unpacked.  Propellant temperature should be determined from ready ammunition on a periodic basis, particularly if there has been a change in the air temperature. 3-8 TC 3-09.81 13 April 2016 Ballistics 3-42. Moisture content of propellant. Changes in the moisture content of propellant are caused by improper protection from the elements or improper handling of the propellant. These changes can affect muzzle velocity. Since the moisture content cannot be measured or corrected for, the propellant must be provided maximum protection from the elements and improper handling. 3-43. Position of propellant in the chamber. In semi-fixed ammunition, the propellant has a relatively fixed position with respect to the chamber, which is formed by the cartridge case. In separate-loading ammunition, the rate at which the propellant burns and the developed muzzle velocity depends on how the cannoneer inserts the charge. To ensure proper ignition of the propellant he must insert the charge so that the base of the propellant is flush against the obturator spindle when the breech is closed. The cannoneer ensures this by placing the propellant flush against the swiss groove (the cutaway portion in the powder chamber). The farther forward the charge is inserted, the slower the burning rate and the lower the subsequent muzzle velocity. An increase in the diameter of the propellant charge can also cause an increase in muzzle velocity. With bag charges, loose tie straps or wrappings have the effect of increasing the diameter of the propellant charge. Propellant charge wrappings should always be checked for tightness, even when the full propellant charge is used. 3-44. Weight of projectile. The weights of like projectiles vary within certain zones (normally termed square weight). The appropriate weight zone is stenciled on the projectile (in terms of so many squares). Some projectiles are marked with the weight in pounds. In general terms, a heavier-than-standard projectile normally experiences a decrease in muzzle velocity. This is because more of the force generated by the gases is used to overcome the initial resistance to movement. A lighter-than-standard projectile generally experiences an increase in velocity. However, when projectiles are fired with higher charges and increased ranges, heavier than standard projectiles may achieve greater ranges. Table F, in the tabular firing tables, lists correction factors for the effect of nonstandard square weights. 3-45. Coppering. When the projectile velocity within the bore is great, sufficient friction and heat are developed to remove the outer surface of the rotating band. Material left is a thin film of copper within the bore and is known as coppering. This phenomenon occurs in weapons that develop a high muzzle velocity and when high charges are fired. The amount of copper deposited varies with velocity. Firing higher charges increases the amount of copper deposited on the bore surfaces, whereas firing lower charges reduces the effects of coppering. Slight coppering resulting from firing a small sample of rounds at higher charges tends to increase muzzle velocity. Erratic velocity performance is a result of excessive coppering whereby the resistance of the bore to projectile movement is affected. Excessive coppering must be removed by ordnance personnel. 3-46. Propellant residue. Residue from burned propellant and certain chemical agents mixed with the expanding gases are deposited on the bore surface in a manner similar to coppering. Unless the tube is properly cleaned and cared for, this residue will accelerate tube wear by causing pitting and augmenting the abrasive action of the projectile. 3-47. Tube conditioning. The temperature of the tube has a direct bearing on the developed muzzle velocity. A cold tube offers a different resistance to projectile movement and is less susceptible to coppering, even at high velocities. In general, a cold tube yields more range dispersion; a hot tube, less range dispersion. 3-48. Additional effects in interior ballistics. The additional effects include tube memory and tube jump.  Tube memory is a physical phenomenon of the cannon tube tending to react to the firing stress in the same manner for each round, even after changing charges. It seems to “remember” the muzzle velocity of the last charge fired. For example, if a fire mission with charge 4 M232A1 is followed by a fire mission with charge 2 M231, the muzzle velocity of the first round of charge 2 may be unpredictably higher. The inverse is also true.  Tube jump occurs as the projectile tries to maintain a straight line when exiting the muzzle. This phenomenon causes the tube to jump up when fired and may cause tube displacement. 13 April 2016 TC 3-09.81 3-9 Chapter 3 SECTION II: TRANSITIONAL BALLISTICS 3-49. Transitional Ballistics. Sometimes referred to as intermediate ballistics, this is the study of the transition from interior to exterior ballistics. Transitional ballistics is complex and involves a number of variables that are not fully understood; therefore, it is not an exact science. What is understood is that when the projectile leaves the muzzle, it receives a slight increase in muzzle velocity from the escaping gases. Immediately after that, its velocity begins to decrease because of drag. SECTION III: EXTERIOR BALLISTICS 3-50. Exterior Ballistics. Exterior ballistics is the science that deals with the factors affecting the motion of a projectile after it leaves the muzzle of a howitzer. At that instant, the total effects of interior ballistics in terms of developed muzzle velocity and spin have been imparted to the projectile. Were it not for gravity and the effects of the atmosphere, the projectile would continue indefinitely at a constant velocity along the infinite extension of the cannon tube. The discussion of exterior ballistics in the following paragraphs addresses elements of the trajectory, the trajectory in a vacuum, the trajectory within a standard atmosphere, and the factors that affect the flight of the projectile. TRAJECTORY ELEMENTS. 3-51. The trajectory is the path traced by the center of gravity of the projectile from the origin to the level point. The elements of a trajectory are classified into three groups--intrinsic, initial, and terminal elements. 3-52. Intrinsic elements. Elements that are characteristic of any trajectory, by definition, are intrinsic elements. (See figure 3-7.)  The origin is the location of the center of gravity of the projectile when it leaves the muzzle. It also denotes the center of the muzzle when the howitzer has been laid.  The ascending branch is the part of the trajectory that is traced as the projectile rises from the origin.  The summit is the highest point of the trajectory.  The maximum ordinate is the difference in altitude (alt) between the origin and the summit.  The descending branch is the part of the trajectory that is traced as the projectile is falling.  The level point is the point on the descending branch that is the same altitude as the origin.  The base of the trajectory is the straight line from the origin to the level point. Figure 3-7. Intrinsic Elements of the Trajectory. 3-53. Initial elements. Elements that are characteristic at the origin of the trajectory are initial elements. (See figure 3-8 on page 3-11.)  When the howitzer is laid, the line of elevation is the axis of the tube 3-10 TC 3-09.81 13 April 2016 Ballistics  The line of departure is a line tangent to the trajectory at the instant the extended projectile leaves the tube.  Jump is the displacement of the line of departure from the line of elevation that exists at the instant the projectile leaves the tube.  The angle of site is the smaller angle in a vertical plane from the base of the trajectory to a straight line joining the origin and the target.  Vertical interval is the difference in altitude between the (or observer) and the target or point of burst.  The complementary angle of site is an angle that is algebraically sum to the angle of site to compensate for the non-rigidity of the trajectory.  Site is the algebraic sum of the angle of site and the complementary angle of site. Site is computed to compensate for situations in which the target is not at the same altitude as the battery.  Complementary range is the number of meters (range correction) equivalent to the number of mils of complementary angle of site.  The angle of elevation is the vertical angle between the base of the trajectory and the axis of the bore required for a projectile to achieve a prescribed range under standard conditions.  The quadrant elevation is the angle at the origin measured from the base of the trajectory to the line of elevation. It is the algebraic sum of site and the angle of elevation. Figure 3-8. Initial Elements of the Trajectory. 3-54. Terminal elements. Elements that are characteristic at the point of impact are terminal elements. (See figure 3-9 on page 3-12.)  The point of impact is the point at which the projectile strikes the target area. (The point of burst is the point at which the projectile bursts in the air.)  The line of fall is the line tangent to the trajectory at the level  The angle of fall is the vertical angle at the level point between the line of fall and the base of the trajectory.  The line of impact is a line tangent to the trajectory at the point of impact.  The angle of impact is the acute angle at the point of impact between the line of impact and a plane tangent to the surface at the point of impact. This term should not be confused with angle of fall. 13 April 2016 TC 3-09.81 3-11 Chapter 3 Figure 3-9. Terminal Elements of the Trajectory. TRAJECTORY IN A VACUUM 3-55. If a round were fired in a vacuum, gravity would cause the projectile to return to the surface of the earth. The path or trajectory of the projectile would be simple to trace. All projectiles, regardless of size, shape, or weight, would follow paths of the same parabolic shape and would achieve the same range for a given muzzle velocity and quadrant elevation. 3-56. The factors used to determine the data needed to construct a firing table for firing in a vacuum are the angle of departure, muzzle velocity, and acceleration caused by the force of gravity. The initial velocity imparted to a round has two components--horizontal velocity and vertical velocity. The relative magnitudes of horizontal and vertical components vary with the angle of elevation. For example, if the elevation were zero, the initial velocity imparted to the round would be horizontal in nature and there would be no vertical component. If, on the other hand, the elevation were 1,600 mils (disregarding the effects of rotation of the earth), the initial velocity would be vertical and there would be no horizontal component. 3-57. Gravity causes a projectile in flight to fall to the earth. Because of gravity, the height of the projectile at any instant is less than it would be if no such force were acting on it. In a vacuum, the vertical velocity would decrease from the initial velocity to zero on the ascending branch of the trajectory and increase from zero to the initial velocity on the descending branch, Zero vertical velocity would occur at the summit of the trajectory. For every vertical velocity value on the upward leg of the ascending branch there is an equal vertical velocity value downward on the descending branch. Since there would be no resistance to the forward motion of the projectile in a vacuum, the horizontal velocity component would be a constant. The acceleration caused by the force of gravity (9.81 m/s) affects only the vertical velocity. TRAJECTORY IN A STANDARD ATMOSPHERE 3-58. The resistance of the air to projectile movement depends on the air movement, density, and temperature. As a point of departure for computing firing tables, assumed conditions of air density and air temperature with no wind are used. The air structure is called the standard atmosphere. 3-59. The most apparent difference between the trajectory in a vacuum and the trajectory in the standard atmosphere is a net reduction in the range achieved by the projectile. A comparison of the flight of the projectile in a vacuum and in the standard atmosphere is shown in figure 3-10 on page 3-13. 3-12 TC 3-09.81 13 April 2016 Ballistics Figure 3-10. Trajectories in a Standard Atmosphere and in a Vacuum. 3-60. The difference in range is due to the horizontal velocity component in the standard atmosphere no longer being a constant value. The horizontal velocity component is continually decreased by the retarding effect of the air. The vertical velocity component is also affected by air resistance. The trajectory in the standard atmosphere has the following characteristic differences from the trajectory in a vacuum:  The velocity at the level point is less than the velocity at the origin.  The mean horizontal velocity of the projectile beyond the summit is less than the mean velocity before the projectile reaches the summit; therefore, the projectile travels a shorter horizontal distance. Hence, the descending branch is shorter than the ascending branch. The angle of fall is greater than the angle of elevation.  The spin (rotational motion) initially imparted to the projectile causes it to respond differently in the standard atmosphere because of air resistance. A trajectory in the standard atmosphere, compared to a trajectory in a vacuum, will be shorter and lower at any specific point along the trajectory for the following reasons:  Horizontal velocity is not a constant value; it decreases with each succeeding time interval.  Vertical velocity is affected by both gravity and the effects of the atmosphere on the projectile.  The summit in a vacuum is midway between the origin and the level point; in the standard atmosphere, it is actually nearer the level point.  The angle of fall in a vacuum is equal to the angle of elevation; in the standard atmosphere, it is greater. RELATION OF AIR RESISTANCE AND PROJECTILE EFFICIENCY TO STANDARD RANGE 3-61. This paragraph concerns only those factors that establish the relationship between the standard range, elevation, and achieved range.  The standard (chart) range is the range opposite a given elevation in the firing tables. It is assumed to have been measured along the surface of a sphere concentric with the earth and passing through the muzzle of a weapon. For all practical purposes, standard range is the horizontal distance from the origin of the trajectory to the level point.  The achieved range is the range attained as a result of firing the cannon at a particular elevation. If actual firing conditions duplicate the ballistic properties and met conditions on which the firing tables are based, then the achieved range and the standard range will be equal.  The corrected range is the range corresponding to the elevation that must be fired to reach the target. 13 April 2016 TC 3-09.81 3-13 Chapter 3 3-62. Air resistance affects the flight of the projectile both in range and in direction. The component of air resistance in the direction opposite that of the forward motion of the projectile is called drag. Because of drag, both the horizontal and vertical components of velocity are less at any given time along the trajectory than they would be if drag was zero (as it would be in a vacuum). This decrease in velocity varies directly in magnitude with drag and inversely with the mass of the projectile. Several factors considered in the computation of drag are as follows:  Air density. The drag of a given projectile is proportional to the density of the air through which it passes. For example, an increase in air density by a given percentage increases drag by the same percentage. Since the air density at a specific place, time, and altitude varies widely, the standard trajectories reflected in the firing tables were computed with a fixed relationship between air density and altitude.  Air temperature. Variations in air temperature cause two separate effects on a projectile. One effect is caused by the inverse relationship of density and temperature (equation of state). This effect is compensated for when density effects are considered. The second effect is regarded as the true temperature effect. It is the result of the relationship between the speed of the projectile and the speed of the air compression waves that form in front of or behind the projectile. These air compression waves move at the speed of sound, which is directly proportional to the air temperature. The relationship between the variation in air temperature and the drag on the projectile is difficult to determine. This is particularly true for supersonic projectiles since they break through the air compression waves after they are formed. As firing tables indicate, an increase in air temperature may increase, decrease, or have no effect on achieved range, depending upon the initial elevation and muzzle velocity of the weapon.  Projectile diameter. Two projectiles of identical shape but of different size will not experience the same drag. For example, a large projectile will offer a larger area for the air to act upon; thus, its drag will be increased by this factor. The drag of projectiles of the same shape is assumed to be proportional to the square of the projectile diameter.  Drag coefficient. The drag coefficient combines several ballistic properties of typical projectiles. These properties include yaw (the angle between the direction of motion and the axis of the projectile) and the ratio of the velocity of the projectile to the speed of sound. Drag coefficients, which have been computed for many projectile types, simplify the work of ballisticians. When a projectile varies slightly in shape from one of the typical projectile types, the drag coefficient can be determined by computing a form factor for the projectile and multiplying the drag coefficient of a typical projectile type by the form factor.  Ballistic coefficient. The ballistic coefficient of a projectile is a measure of its relative efficiency in overcoming air resistance. An increase in the ballistic coefficient reduces the effect of drag and consequently increases range. The reverse is true for a decrease in the ballistic coefficient. The ballistic coefficient can be increased by increasing the ratio of the weight of the projectile to the square of its diameter. It can also be increased by improving the shape of the projectile. DEVIATIONS FROM STANDARD CONDITIONS 3-63. Firing tables are based on actual firings of a piece and its ammunition correlated to a set of standard conditions. Actual firing conditions, however, will never equate to standard conditions. These deviations from standard conditions, if not corrected for when computing firing data will cause the projectile to impact at a point other than the desired location. Corrections for nonstandard conditions are made to improve accuracy.  Range effects. Some of the deviations from standard conditions affecting range are:  Muzzle velocity.  Projectile weight.  Range wind.  Air temperature.  Air density.  Rotation of the earth.  Propellant temperature. 3-14 TC 3-09.81 13 April 2016 Ballistics  Deflection effects. Some of the deviations from the standard conditions affecting deflection are:  Drift.  Crosswind.  Rotation of the earth. DISPERSION AND PROBABILITY 3-64. If a number of rounds of ammunition of the same caliber, lot, and charge are fired from the same position with identical settings used for deflection and quadrant elevation, the rounds will not all impact on a single point but will fall in a scattered pattern. In discussions of artillery fire, this phenomenon is called dispersion, and the array of bursts on the ground is called the dispersion pattern. CAUSES OF DISPERSION 3-65. The points of impact of the projectiles will be scattered both in deflection and in range. Dispersion is the result of minor variation from round to round (caused by inherent systemic errors) and must not be confused with variation in point of impact caused by Human Errors or Constant Errors. Human errors are mistakes made by any member of the gunnery team and can be minimized through training and supervision. Constant errors are errors that are known and are constant throughout the mission. Corrections to compensate for the effects of constant errors can be determined from the TFT. Inherent errors are beyond control or are impractical to measure. Examples of inherent errors are as follows:  Conditions in the bore. The muzzle velocity achieved by a given projectile is affected by the following:  Variations in the weight of the projectile form of the rotating band, and moisture content and temperature of the powder grains.  Variations in the placement of propellant.  Differences in the rate of ignition of the propellant.  Variations in the arrangement of the powder grains contained inside the propellant increment.  Variations in the ramming of the projectile.  Variations in the temperature of the bore from round to round. For example, variations in the bourrelet and rotating band may cause inaccurate centering of the projectile, which can result in a loss in achieved range because of instability in flight.  Conditions in the carriage. Deflection and elevation are affected by the following:  Play (looseness) in the mechanisms of the carriage.  Physical limitations of precision in setting values of deflection and quadrant elevation on the respective scales.  Non-uniform reactions to firing stress.  Conditions during flight. The flight of the projectile may be affected by the difference in air resistance created by variations in the weight, achieved muzzle velocity, and projectile. Also, the projectile may be affected by variations in wind, air density or air pressure, and air temperature from round to round. 3-66. The distribution of bursts (dispersion pattern) in a given sample of rounds is roughly elliptical (Figure 3-11) with the long axis parallel to the line of fire. 3-67. A rectangle constructed around the dispersion area containing all usable rounds is called the dispersion rectangle. (See figure 3-11 on page 3-16.) Note: 0.7% of rounds fired are erratic and do not impact within 4 probable errors in range (PER). The seven erratic rounds will impact within 5.8 PER. 13 April 2016 TC 3-09.81 3-15 Chapter 3 MEAN POINT OF IMPACT 3-68. For any large number of rounds fired, the average (or mean) location of impact can be determined by drawing a diagram of the pattern of bursts as they appear on the ground. A line drawn perpendicular to the line of fire can be used to divide the sample rounds into two equal groups. Therefore, half of the rounds will be over this line when considered in relation to the weapon. The other half of the rounds will be short of this line in relation to the weapon. This dividing line represents the mean range of the sample and is called the mean range line. A second line can be drawn parallel to the line of fire, again dividing the sample into two equal groups. Half of the rounds will be to the right of this line, and half will be to the left. This line represents the mean deflection of the sample and is called the mean deflection line. (See figure 3-11.) The intersection of the two lines is the mean point of impact (MPI). Figure 3-11. Dispersion Rectangle. PROBABLE ERROR 3-69. Probable error is nothing more than an error that is exceeded as often as it is not exceeded. For example, in figure 3-12 (on page 3-17), consider only those rounds that have impacted over the mean range line (line AB). These rounds all manifest errors in range, since they all impacted over the mean range line. Some of the rounds are more in error than others. At a point beyond the MPI, a second line can be drawn perpendicular to the line of fire to divide the "overs" into two equal groups (line CD, figure 3-12). When the distance from the MPI to line CD is used as a measure of probable error, it is obvious that half of the overs show greater magnitude of error than the other half. This distance is one probable error in range. The range probability curve expresses the following:  In a large number of samples, errors in excess and errors in deficiency are equally frequent (probable) as shown by the symmetry of the curve.  The errors are not uniformly distributed. Small errors occur more frequently than large errors as shown by the greater number of occurrences near the mean point of impact. 3-16 TC 3-09.81 13 April 2016 Ballistics Figure 3-12. Probable Errors. DISPERSION ZONES 3-70. If the dispersion rectangle is divided evenly into eight zones in range with the value for 1 probable error in range (PER) used as the unit of measure, the percentage of rounds impacting within each zone is as indicated in figure 3-13. The percentage of rounds impacting within each zone has been determined through experimentation. By definition of probable error, 50 percent of all rounds will impact within 1 probable error in range or deflection of the mean point of impact (25 percent over and 25 percent short or 25 percent left and 25 percent right). Figure 3-13. Dispersion Zones. RANGE PROBABLE ERROR 3-71. The values for range probable error at various ranges are given in Table G of the tabular firing tables (TFT). These values may be used as an index of the precision of the piece at a particular charge and range. The values for range probable error are listed in meters. Firing Table (FT) values have been determined on the basis of actual firing of ammunition under controlled conditions. For example, FT 155-AM-3 shows that the value of range probable error for charge 4H M232A1 at a range of 6,000 meters is 15 meters. On the basis of the dispersion rectangle, 50 percent of the rounds will impact within 15 meters (over and short) of the mean range line, 82 percent will impact within 30 meters (over and short), 96 percent will impact within 45-meters (over and short), and 100 percent of usable rounds will impact within 60 meters. 13 April 2016 TC 3-09.81 3-17 Chapter 3 FORK 3-72. The term fork is used to express the change in elevation (in mils) needed to move the mean point of impact 4 probable errors in range. The values of fork are listed in Table F of the firing tables. For example, FT 155-AM-3 shows that the value of fork for a howitzer firing charge 4H M232A1 at a range of 6,000 meters is 1 mil. On the basis of the value for probable error in range (paragraph 3-72), adding 1 mil to the quadrant elevation would cause the MPI to move 60 meters. This is based off of the previous argument where we determined 1 PER for 4H M232A1 at range 6,000 meters to be 15 meters. Fork is used in the computation of safety data. DEFLECTION PROBABLE ERROR 3-73. The values for probable error in deflection (PED) are listed in Table G of the firing tables. For artillery cannons, the deflection probable error is considerably smaller than the range probable error. Values for PED are listed in meters. With the same parameters as those used in paragraph 3-72, the deflection probable error is 3 meters. Therefore, 50 percent of the rounds will impact within 3 meters of the mean deflection line (left and right); 82 percent, within 6 meters (left and right); 96 percent, within 9 meters (left and right); and 100 percent, within 12 meters. TIME-TO-BURST PROBABLE ERROR 3-74. The values of time-to-burst probable error (PETB) (Figure 3-15) are listed in Table G of the firing tables. Each of these values is the weighted average of the precision of a time fuze timing mechanism in relation to the actual time of flight of the projectile. For example, if a 155-millimeter (mm) howitzer fires charge 4H M231A1 at a range of 6,000 meters, the value for probable error in time to burst is 0.04 second. As in any other dispersion pattern, 50 percent of the rounds will function within 0.04 second; 82 percent, within 0.08 second; 96 percent, within 0.12 second; and 100 percent within 0.16 second of the mean fuze setting. HEIGHT-OF-BURST PROBABLE ERROR 3-75. With the projectile fuzed to burst in the air, the height-of-burst probable error (PEHB) (Figure 3-15) is the vertical component of 1 time-to-burst probable error. The height-of-burst probable error reflects the combined effects of dispersion caused by variations in the functioning of the time fuze and dispersion caused by the conditions described in paragraph 3-78 The values listed (in meters) follow the same pattern of distribution as for those discussed for range dispersion. These values are listed in Table G of the firing table. RANGE-TO-BURST PROBABLE ERROR 3-76. Range-to-burst probable error (PERB; figure 3-14 on page 3-19) is the horizontal component of 1 time-to-burst probable error. When this value is added to or subtracted from the expected range to burst, it will produce an interval along the line of fire that should contain 50 percent of the rounds fired. These values are listed in Table G of the firing tables. 3-18 TC 3-09.81 13 April 2016 Ballistics Figure 3-14. Comparison of PEHB, PERB, and PETB. SECTION IV: TERMINAL BALLISTICS 3-77. Terminal ballistics may be defined as the study of the effects of projectiles on a target. The theory of terminal ballistics is relatively new compared to the theory of internal and external ballistics. The techniques of investigation for impact on solid targets consist primarily of empirical relations (based on experiments), analytical models, and computer simulations. In terminal ballistics, we are dealing with the shock caused by the detonation of the high-explosive (HE) filler. The effects are most pronounced if the shell penetrates the surface of a target before detonation. TARGET ANALYSIS AND MUNITION EFFECTS (WEAPONEERING) 3-78. Target analysis is the examination and evaluation of an enemy target situation to determine the most suitable weapon, ammunition, and method required to defeat, neutralize, or otherwise disrupt, delay, or limit the enemy. Not only does target analysis involve determining the amount and type of ammunition required to inflict a given damage (or casualty) level on a particular target, it also involves a continuous process of consultation and cooperation between the commander and the FDO. In Joint doctrine this is referred as weaponeering. Weaponeering can be defined as the process of determining the quantity of a specific type of weapon required to achieve a specific level of target damage; considering factors such as target vulnerability, weapon effects, munitions delivery accuracy, desired effect, probability of kill (PK), weapon reliability, etc (61 JTCG/ME-88-7). TARGET ANALYSIS 3-79. The amount of time devoted to target analysis and the thoroughness of the analysis depends on the following:  Amount of target information.  Weapons and ammunition available to attack the target.  Urgency of the engagement. 13 April 2016 TC 3-09.81 3-19 Chapter 3 DETERMINING THE PRECEDENCE OF ATTACK 3-80. When an FDO receives a fire mission, his options include the following (see figure 3-15 for determining the precedence of attack):  Attack the target immediately.  Defer attacking the target until an existing fire mission is complete.  Pass the fire mission to another FDC.  Request reinforcing fires.  Deny the mission. Figure 3-15. Determining the Precedence of Attack. 3-81. An FDO selects a particular precedence of attack after considering the following:  Call for fire.  Terrain. 3-20 TC 3-09.81 13 April 2016 Ballistics  Target location.  Weather.  Target characteristics.  Units available.  Commander’s criteria.  Availability of corrections.  Munitions effects.  Enemy target acquisition.  Commander’s intent.  Ammunition availability. COMMANDER’S GUIDANCE. 3-82. Commander’s Guidance. All phases of target analysis are conducted within constraints established by the commander. In determining the precedence for attacking a target, primary consideration is given to the commander’s target priorities.  Attack guidance matrix. The commander’s target priorities are organized into an attack guidance matrix that lists the type of target, when to attack, degree of destruction, and any restrictions. Figure 3-16 is an example of a commander’s attack guidance matrix. The following example explains how it would be used. EXAMPLE Your FDC received a call for fire, and the target description was an ammunition dump. While processing this mission. You received another call for fire requesting fires on an infantry platoon. Referring to the attack guidance matrix, you determine that the infantry platoon is a higher priority. In this case, you process this mission first. Upon completion of this mission, you would fire on the ammunition dump. CATEGORY HIGH PAYOFF WHEN HOW RESTRICTIONS 1(C3) 25,29,30,34 I N/EW Coordinate attack with EW 2 (FS) 1,2,5,18 I N Plan all calibers greater than 122mm 3(MAN) 46,48,50,51 I 10% 4(ADA) 63,64 A N 5(ENGR) 69,70 P N Not high-payoff target 6(RSTA) 14,16,17,84,85,107 A D Not high-payoff target 7(REC) 91,92 A S/EW Coordinate attack with EW 8(N/NH) 77,79 P D Forward targets to division 9(POL) 115,116 A D 10(AMMO) 120,121 A N 11(MAINT) A S 12(LIFT) A S 13(LOG) LEGEND: 118 A= ADA= C3= D= engr= FS= as acquired Air defense artillery Command, control, and communications Destroy engineer fire support A I= log= man= N= N Not high-payoff target immediate logistics maneuver neutralized N= Neutralized REC= radio electronic combat RSTA= reconnaissance, surveillance and target acquisition S= suppress Figure 3-16. Attack Guidance Matrix Example. Note: For a more detailed discussion on the attack guidance matrix, see ATP 3-09.42. 13 April 2016 TC 3-09.81 3-21 Chapter 3  Target effects categories. On the basis of ammunition constraints, a commander also specifies the type of effects he desires against specific target categories. The three target effects categories are as follows:  Destruction. Destruction puts the target out of action permanently. 30 percent casualties or materiel damage inflicted during a short time span normally renders a unit permanently ineffective. Direct hits are required to destroy hard materiel targets. Targets must be located by accurate map inspection, indirect fire adjustment, or a TA device. Destruction usually requires a large amount of ammunition from many units.  Neutralization. Neutralization of a target knocks the target out of the battle temporarily. Casualties of 10 percent or more neutralize a unit. The unit is effective again when the casualties are replaced and/or damage is repaired. Neutralization fires are delivered against targets located by accurate map inspection, indirect fire adjustment, or a TA device. The assets required to neutralize a target vary according to the type and size of the target and the weapon-ammunition combination.  Suppression. Suppression of a target limits the ability of enemy personnel to perform their mission. Firing HE, variable time (VT) fuze reduces the combat effectiveness of personnel and armored targets by creating apprehension and surprise and by causing tracked vehicles to button up. Smoke is used to blind or confuse. The effect of suppressive fires usually lasts only as long as the fires are continued. This type of fire is used against likely, suspected, or inaccurately located enemy units where time is essential. It can be delivered by small delivery units or means and requires little ammunition. TARGET CHARACTERISTICS. 3-83. Targets encountered on the battlefield vary considerably in composition, degree of protection, shape, mobility, and recuperability. For simplicity, targets are divided into four categories (table 3-1) to compare the effectiveness of particular weapons and rounds. Examples are listed for each category. Under certain conditions, some examples could be listed in more than one category. For example, a motorized rifle battalion could be listed under the first category and the fourth category. Table 3-1. Categories of Targets. CATEGORY Area (Personnel) Small (Personnel) Small (Material) (Point) Area(Materiel) EXAMPLE Squad Platoon Battery/Company Observation post Small Patrol Command Post Tank Armored personnel carrier Bunker, machine gun Armored formation Truck park Ammunition Dump 3-84. For personnel targets in particular, the posture of the target is extremely important. Normally, target postures used for personnel targets are standing, prone, and in fighting positions. For computation, it is assumed that the personnel are wearing helmets and that personnel in fighting positions are in a crouching position. In describing posture of a target, consider the protection afforded by the terrain. For example, an infantry platoon may be attacking in a standing posture. However, irregular terrain may provide protection equivalent to the prone position. Usually, personnel targets seek a more protective posture during an engagement; for example, from a standing to a prone position. This change is called posture sequencing. Posture sequencing causes considerable degradation of effects as additional volleys are fired and is the 3-22 TC 3-09.81 13 April 2016 Ballistics reason for the continual emphasis on surprise or mass fires. For the purposes of analysis, personnel targets in the offense are considered to be one-half standing and one-half prone during the first volley of fire and all prone for subsequent volleys. In a defensive configuration, personnel targets are considered to be onehalf prone and one-half in fighting positions during the initial volley and all in fighting positions for subsequent volleys. 3-85. A target must be analyzed to determine its weak points. Where the target is most vulnerable and what fires will best exploit its weaknesses are influenced by the degree of damage desired. Often there is a tendency to overkill the target when less combat power would suffice. On the basis of the commander’s Guidance criteria, the FDO must ascertain the degree of effects needed (destruction, neutralization, suppression) to support the tactical plan. The acceptable degree of damage is the level that yields a significant military advantage. For example, fire from a heavily protected machine-gun emplacement may be silenced by obscuration through smoke and subsequent engagement by direct fire as opposed to the expenditure of a large number of HE rounds required for its destruction.  Target location. The FDO must check the target location relative to friendly forces, fire support coordinating measures, zones of fire, and registration transfer limits. Target location accuracy is also considered. The range affects the choice of units to fire and charge selection. The terrain around the target may influence ammo selection or type of trajectory. High intervening crests may require selection of a lower charge or high angle.  Target characteristics. The size of the target affects the number of units to fire, the type of sheaf, the selection of ammo, and the number of rounds in the fire for effect. The type of target (troops, vehicles, hard, soft) influences the ammo type and amount, the priority placed on the mission, and whether surprise fire (for example, time on target) is possible.  Ammo availability. The FDO must consider the amount and type of ammunition available and the controlled supply rate.  Units available. The number of units available not only affects which units are used, but also the type of attack. Sweep and/or zone fire or other techniques may be needed to cover large targets when enough units are not available.  Commander’s Guidance or commander’s intent. Restrictions on ammo, operations order (OPORD), and SOPs may govern the selection of units and ammunition, target priority, and method of attack.  Call for fire. The FDO must consider the observer’s request carefully since he is observing the target and talks directly to the maneuver commander. The observer’s requests honored when possible. The call for fire will also include information on the target activity (for example, attacking, defending, and digging in).  Munitions effects. The FDO most often relies on the Commander Guidance or experience.  Availability of corrections. The availability of corrections to firing data for non-standard conditions is a guiding factor in the choice of charge and munitions, since it directly affects the ability to provide accurate first round fire for effect.  Enemy target acquisition capability. Knowledge of the current enemy counter-battery radar and sound ranging capabilities allows the FDO to attack the target in a manner most likely to evade detection.  Terrain. The terrain in the target area has a direct effect on the vulnerability of the target. Rugged terrain affords considerable natural cover and makes target location difficult. Certain terrain provides complete protection from some angles of approach but not others and thus influences the unit and munitions to be employed. The nature of the vegetation in the target area should be considered when selecting ammunition.  Weather. Weather is of little consequence in evaluating a target to attack with fuze quick or time. However, precipitation and wind are of particular importance in evaluating a target to attack with improved conventional munitions (ICM), smoke, family of scatterable mines (FASCAM), or illumination projectiles. Low clouds, thick fog, surface water, and rain degrade the effectiveness of VT fuze. 13 April 2016 TC 3-09.81 3-23 Chapter 3 DETERMINING MOST SUITABLE WEAPON AND AMMUNITION 3-86. When an FDO decides to attack a target, he selects a weapon-ammunition combination that achieves the desired effect with a minimum expenditure of available ammo. Figure 3-17 depicts weaponammunition selection. Figure 3-17. Weapon-Ammunition Selection. MUNITIONS. 3-87. Type and quantity available. The nature of the target, its surroundings, and the desired effects dictate the type and amount of ammo to use. For a detailed discussion of ammo and fuzes, refer to Technical Manual (TM) 43-0001-28. The ammo resupply system sometimes rules out the best ammo selection. For example, extensive smoke fires may be needed to screen maneuver movement, but such fires may cause a resupply problem. Some fires require more ammo than others. Suppression and neutralization fires normally use less ammo than destruction fires. Destruction fire is 1. An element of the method of engagement portion of the call for fire requesting destruction fire. 2. Fire delivered for the sole purpose of destroying materiel. 3-88. Troop safety. Troop safety is a major concern in considering the weapon-ammunition selection for firing close-in targets. The FDO must ensure that fires do not endanger friendly troops, equipment, and facilities. 3-89. Residual effects in target area. The supported unit must be advised of the residual effects from certain munitions. For example, the self-destruct times from FASCAM munitions may preclude the desired movement of supported units through a particular area. Weather changes may alter choices of certain munitions (smoke, illumination, and white phosphorous). The incendiary effects of certain munitions may 3-24 TC 3-09.81 13 April 2016 Ballistics make areas untenable for supported forces. However, these effects can also deny the enemy use of selected terrain. 3-90. Effectiveness. When properly delivered against appropriate targets, artillery fire support can be the decisive factor in a battle. The FDO must ensure that the desired result is attained from every mission. To match a munitions to a target, the FDO must know what damage a munitions can produce and the damage required to defeat the target. The lethality of munitions must be matched to the specific vulnerability of the target. Thus, the FDO must understand the damage potential (blast, cratering, fragmentation, incendiary, and penetration) of specific munitions. Specific information regarding the effects of various munitions is found in the appropriate Joint Munitions Effectiveness Manual/Air-to-Surface (JMEM/AS) WEAPONEERING GUIDE 61 Joint Technical Coordination Group/Munitions Effectiveness (JTCG/ME) 88-7. WEAPONS. 3-91. Caliber and type available. In certain instances, an FDO may control the fires of reinforcing (R) or general support reinforcing (GSR) units that fire a different caliber. The FDO must have a thorough knowledge of the characteristics, capabilities, and vulnerabilities of each weapon system. Weapons with slow rates of fire and poor delivery accuracy are best suited for long-range fires. Weapons with rapid rates of fire and good delivery accuracy are suited for close fires. 3-92. System response time. An FDO must ascertain the urgency of each fire mission. A fire mission is 1. The specific assignment given to a fire unit as part of a definite plan. 2. An order used to alert the weapon/battery area and indicate that the message following is a call for fire. Small and medium weapons have a quicker firing response time than heavy weapons. Fire missions transmitted by the brigade combat team’s field artillery battalion to reinforcing or GSR units require more processing time than those transmitted directly to the firing batteries of the battalion. 3-93. Predicted fire capability. The FDO must know the current survey, registration, and met status of all firing units under his control. FFE missions should be assigned to units that have the best predicted fire capability. DETERMINING THE METHOD OF ATTACK 3-94. The final step in the FDO’s target analysis is the selection of a method of attack. The FDO selects a method of attack that ensures target area coverage and desired target effects. To determine the best method of attack, the FDO must consider aim-points, density, and duration of fire; Figure 3-18 shows the methodof-attack selection considerations. Figure 3-18. Considerations in Selecting a Method of Attack. 3-95. To determine the best method of attack, the FDO must consider:  Aim-points. Normally, the size of the area to be attacked depends on the size of the target or the size of the area in which the target location is known or suspected. A single aiming point in the 13 April 2016 TC 3-09.81 3-25 Chapter 3 center of the target is used to attack small targets. For attacking large targets, multiple aim-points are designated to distribute the fires and ensure adequate coverage. Appendix G gives procedures for establishing multiple aim-points.  Density. For most targets, uniform density of fires is needed. Several techniques for indirect fire weapons produce such results. These include zone and sweep fires either from a single unit or simultaneous attack by multiple units on different portions of the target.  Duration. Accurate surprise fires produce the most effective results. Time on target procedures place initial rounds from all units on the target at the same time and achieve the greatest surprise. While intense fires of short duration generally produce the best results, the tactical situation may require that fires be continued over a longer period of time. Some examples are harassing and interdiction fires, screening smoke, continuous illumination, and suppressive fires supporting a maneuver final assault on an objective. PREDICTING WEAPONS AND MUNITIONS EFFECTS 3-96. The most important step in performing target analysis (weaponeering) is determining the number and type of rounds required to produce the desired effects on a target. The time available to perform the target analysis largely determines the tools used to predict effects. An analyst at the division fire support level can use the JMEM/AS for guidance while the FDO at battalion or battery level, because of time constraints, can use the Commander Guidance. JOINT MUNITIONS EFFECTIVENESS MANUALS WEAPONEERING SYSTEM (JWS) 3-97. Overview. Joint Munitions Effectiveness Manuals Weaponeering System (JWS) is a complete guide to conventional weaponeering. Its purpose is to provide all essential references to produce weapons effectiveness for conventional weapons. The JWS product contains the information from many of the JTCG/AS JMEMs and Special Reports in a content-based, hyperlink configuration. Many of the JMEM/AS manuals are no longer being published separately. Users are directed to the JWS product. Also included are the databases and applications needed to look up or produce weapons effects estimates. The information on the following topics and weaponeering applications are included on the JWS product. 3-98. Characteristics. For detailed characteristics of various types of inventory nonnuclear weapons, see Weapons of JWS. Data are presented for general-purpose (GP) bombs, clusters, guns and rockets, fire and incendiary bombs, and special-purpose weapons, as well as, weapon fuzes. 3-99. Included Data. Data include a description of the weapon or warhead; carriage and suspension data; detailed information on warhead fragmentation, to include number of fragments, mass, and velocity for polar zones 0 to 180 degrees (0 degrees represents the nose of the warhead); explosive type and weight; and line drawings of the weapon showing length, diameter, and center of gravity. A detailed explanation of fragmentation and blast phenomena is provided in “General-Purpose (GP) Munitions” in Weapons of JWS. 3-100. Compatibility and Reliability. Weapon fuzing reliability and compatibility data are given for all combinations of inventory items. Programs with available data are provided below. QUICK REFERENCE TABLES 3-101. If JMEMs are not available, the FDO can use the guide for cannon attack of typical targets (table 3-2 on page 3-27). The table lists selected personnel and materiel targets and indicates the order of effectiveness for each shell-fuze combination. Targets not indicted should be equated to targets that are listed. The table can be used for all calibers. 3-26 TC 3-09.81 13 April 2016 Ballistics Table 3-2. Guide for Cannon Attack of Typical Targets. TARGET TYPE PERSONNEL In Open or In fighting position without overhead cover In Fighting position with overhead cover In dugouts or caves Attacking battery position VEHICLES2 Tanks Armored Personnel Carriers OBSERVATION WEAPONS PROJECTILE HE FUZE RESULT DESIRED Observed and/or All HE unobserved Proximity (VT), Time Destruction All HE All HE Proximity (VT), Time Quick, proximity Time Neutralization Suppression All APICM M577 Destruction All Observed All APICM HE Quick/delay (ricochet) Neutralization Neutralization Observed Observed Observed All HE All APICM All APICM All (preferably HE 155mm or larger) 105mm ALL Beehive HE APICM All HE Proximity, Time, delay, quick Suppression M577 M577 Neutralization Suppression Delay/quick Destruction Time Destruction Proximity, Time Suppression Observed and/or unobserved Observed Observed Direct Fire Observed Observed and/or unobserved 155mm 155mm 155mm 105mm All 155 mm DPICM FASCAM Copperhead HEP, HEP-T, HEAT HE APICM DPICM M577 M577 N/A N/A Proximity, Time M577 Suppression N/A Destruction Destruction Suppression Neutralization REMARKS Massing is required. 1 TOT missions are most effective. First volley is most effective. Massing required except for small targets. Response time is critical against active targets. Preferred fuze is proximity Massing is required on large target. TOT missions are most effective. Cannon battery volleys are sufficient. Massing is required. TOT mission are most effective. Consider use of WP to drive personnel out of fighting positions. Response time is critical against active targets. Proximity fuze is proffered. Consider use of smoke for obscuration. Massing is required. TOT mission are most effective. Consider use of ICM on intermittent basis for increased effectiveness. Use direct fire or assault techniques. Fire HE quick at intervals to clear away camouflage, earth cover, and rubble Set fuze to detonated on the ascending branch of the trajectory for close in defense of battery area Fire projectile HE to force tanks to button up and personnel outside to take cover or disperse. WP may blind vehicles drivers, and fires maybe started from incendiary effect on outside fuel tank. WP or fires may obscure adjustment. DPICM is preferred munitions for unobserved fire. Both anti-tank and antipersonnel projectiles should be used. Force vehicles to button up and personnel outside to take cover or disperse 13 April 2016 TC 3-09.81 3-27 Chapter 3 Table 3-2. Guide for Cannon Attack of Typical Targets (continued). TARGET TYPE Trucks WEAPONS Anti-tank missile OBSERVATION WEAPONS PROJECTILE HE FUZE Observed Observed and/or unobserved 155mm 155mm All 155 mm FASCAM Copperhead HE DPICM M577 N/A Proximity, Time M577 Observed All HE Quick AIR DEFENSE ZSU-23-4, SA6 Observed and/or unobserved All 155mm HE DPICM Proximity M577 SA8,9 Observed All All Towed FA, Unobserved All Mortars, multiple rocket launcher All HE HE HE, WP APICM Quick Quick Proximity, Time M577 Self-propelled FA Unobserved battery Surface to surface missile Unobserved MISCELLANEOUS Radar Unobserved Artillery command and observation post Observed Command post Unobserved 155mm All 155 mm 155mm 155 mm FASCAM HE, WP DPICM FASCAM HE DPICM All 155mm All 155mm All 155mm HE DPICM HE DPICM HE DPICM M577 Proximity, Time M577 M577 Proximity, Time M577 Quick, time, proximity M577 Quick M577 Proximity, Time M577 RESULT DESIRED N/A Destruction Destruction REMARKS See remarks for Tanks. ICM is preferred munitions Destruction Suppression Response time is critical. Intermittent fire may be required. Change to fuze proximity or DPICM for materiel damage if anti-tank guided missile platform on BRDM is raised. Firepower kill Firepower kill Suppression Firepower kill Firepower kill N/A Suppression Suppression N/A Firepower kill Firepower kill Smoke may also be used to obscure gunner’s line of sight to friendly aircraft. ICM is preferred munition. Consider converge sheaf if weapon is point target and accurately located Response time is critical. Intermittent fire may be required. See above WP is used to ignite materiel. See personnel targets for result desired. See personnel targets section for result desired. TOT mission are most effective. Massing is usually required. USE ADAM projectile in conjunction with HE or ICM for sustained effects. WP is used to ignite materiel ICM is preferred munition. Use ADAM projectile in conjunction with HE or ICM for sustained effects. Use converge sheaf if time and target location accuracy permit. TLE in excess of 200 meters requires massing of fires. ICM is preferred munition. Firepower kill Suppression Neutralization or destruction N/A Use converged sheaf if time and target location accuracy permit. TLE in excess of 200 meters requires massing of fires. ICM is preferred munition. Intermittent fire may be required. HE is preferred munition when response time is critical. Use ADAM for sustained effects. When target contains personnel and flight materiel targets, DPICM is preferred munition. 3-28 TC 3-09.81 13 April 2016 Ballistics Table 3-2. Guide for Cannon Attack of Typical Targets (continued). TARGET TYPE OBSERVATION WEAPONS PROJECTILE HE FUZE RESULT DESIRED REMARKS Supply Unobserved All Installation HE, WP Quick Fires Large target location errors require massing to ensure target converge. Boats Observed All HE Time Suppression Attack as moving personnel target Bridge Observed and/or unobserved Observed All (preferably HE 155mm) 155mm Copperhead Quick, concrete piercing, delay N/A Destruction Direction of fire preferably with long axis of the bridge. Destruction of permanent bridges is best accomplished by knocking out bridge support. Use fuze quick for wooden or pontoon bridges. Fortifications Observed All (preferably HE 155mm) Quick, concrete piercing, delay Destruction Use highest practical charge in assault and direct fire. 155mm Copperhead N/A 1Target, regardless of the type, with an estimated target radius greater than 150 meters usually require massing for effective attack. 2The first objective of firing on moving vehicles is to stop the movement. For purpose, a deep bracket is established so that the target will not move out of the initial bracket during adjustment. Speed on adjustment is essential. If possible, the column should be stopped at a point where vehicles cannot change their route and where one stalled vehicle will cause others to stop. Vehicles moving on a road can be attacked by adjusting on a point on the road and then timing the rounds fired so that they arrived at that point when a vehicle is passing it. A firing unit, if available, may fire at different points on the road simultaneously. Legend: ADAM – Area Denial Artillery Munition APICM – Anti-personnel Improved Conventional Munition DPICM – Dual Purpose Improved Conventional Munition FA – field artillery FASCAM – Family of Scatterable Mines HE – High Explosive HEAT – High Explosive Anti-tank HEP – High Explosive Plastic HEP-T – High Explosive Plastic – Tracer ICM – Improved Conventional Munition MM - millimeter TLE – Target Location Error TOT – Time on Target VT – Variable Time WP – White Phosphorous 3-102. The expected area of coverage table (table 3-3) can be used to determine the appropriate size of a battery one volley or battalion one volley of both HE and ICM for the various caliber weapon systems. The FDO can use table 3-3 to determine the size target that can be attacked by use of battery or battalion volleys. The density of coverage is not considered, but the density of coverage of ICM is much greater than that of HE. Table 3-3. Expected Area of Coverage (Meters). Munitions APICM (Anti-personnel Improved Conventional Munition) Square Circle (radius) High Explosive Square Circle (radius) 105mm Battery 1 Round Battalion 1 Round 250 x 250 380 x 380 140 215 Battery 1 Round Battalion 1 Round 248 x 248 380 x 380 140 215 155mm Battery 1 Round Battalion 1 Round 266 x 266 390 x 390 150 220 Battery 1 Round Battalion 1 Round 275 x 275 390 x 390 155 220 13 April 2016 TC 3-09.81 3-29 Chapter 3 3-103. The expected fraction of casualties or personnel table (table 3-4) can be used to determine the optimum method of attacking a personnel target of 50 meters radius to achieve the commander’s criteria. Table 3-4 cannot be used for material targets. Table 3-4. Expected Percentage of Casualties or Personnel. PROJECTILE IF TARGET RADIUS IS 50 METERS, THEN APICM HE/VT HE/PD 105mm Battery 1 Round 07 07 04 Battalion 1 Round 20 20 12 155mm Battery 1 Round 15 05 03 Battalion 1 Round 35 16 11 Legend: APICM – Anti-personnel Improved Conventional Munition HE – High Explosive mm - millimeter PD – Point Detonating VT – Variable Time MUNITIONS EFFECTS 3-104. The various munitions effects are described below, by munition type. Considerations include howitzer availability and fuze combinations. HIGH EXPLOSIVE (HE). 3-105. High Explosive. The use of the HE with its many different fuze combinations (point-detonating [PD]-Super-quick or Delay, Time, or variable time [VT]) is very effective against personnel targets except when they have a high degree of protection. The HE projectile is available for the 105-mm and 155-mm howitzers. HIGH EXPLOSIVE ROCKET-ASSISTED PROJECTILES (HERA) 3-106. HERA Projectile. This projectile has two distinct advantages over normal HE--increased range and fragmentation. The rocket-assisted projectile (RAP) round is primarily used against antipersonnel and material targets at increased ranges. The RAP round is available for the 105-mm and 155-mm howitzers. They are designed to extend the range of the howitzers. The basic rocket-assisted projectiles are filled with HE material. They produce blast and fragmentation in the target area. Computation procedures for all basic HE RAPs are identical. Firing tables may be available for both the rocket on and rocket off mode, depending on the projectile. SMOKE 3-107. Smoke. There are four different types of smoke in our inventory: Hexachloroethane (HC) smoke, colored smoke, white phosphorus, and M825/M825A smoke. The three types of smoke projectiles area as follows:  Hexachloroethane (HC) smoke projectiles are available for 105-mm and 155-mm howitzers. They are used for screening, obscuration, spotting, and signaling purposes. The projectile has no casualty-producing effects. This base-ejection projectile is ballistically similar to the M107 family of projectile. It is fitted with a base ejecting time fuze. The round expels smoke canisters that emit smoke for a period of 40 to 90seconds.  Burster-type white phosphorus. White phosphorus projectiles are available for 105-mm and 155-mm howitzers. They are bursting-tube type projectiles that can be fired with pointdetonating (PD) or bursting time fuzes. The projectile has an incendiary-producing effect and is ballistically similar to the HE (105mm) or M107 (155mm) family of projectile. Normally, shell white phosphorous (WP) is employed for its incendiary effect. The projectile also can be used for screening, spotting, and signaling purposes.  M825/A1 white phosphorus. The M825/A1 WP projectile is an FA-delivered 155-mm baseejection projectile designed to produce a smoke screen on the ground for duration of 5 to15 3-30 TC 3-09.81 13 April 2016 Ballistics minutes. It consists of two major components--the projectile carrier and the payload. The projectile carrier delivers the payload to the target. The payload consists of 116 WP-saturated felt wedges. The smoke screen is produced when a predetermined fuze action causes ejection of the payload from the projectile. After ejection, the WP-saturated felt wedges in the payload fall to the ground in an elliptical pattern. Each wedge then becomes a point or source of smoke. The M825/A1 is ballistically similar to the M795 family of projectiles. ILLUMINATION 3-108. Visible light (VL) Illumination. The illumination projectile is primarily used for night attack or defense, as a ground marking round for a particular target, and for harassment. The illumination projectile is available for the 105-mm and 155-mm howitzers. 3-109. Infrared (IR) illumination provides illumination that is visible through night sights, but not to the naked eye. The 155-mm infrared (IR) illumination round provides infrared illumination out to 17 kilometers for a minimum of 120 seconds. ANTIPERSONNEL IMPROVED CONVENTIONAL MUNITIONS 3-110. Antipersonnel Improved Conventional Munitions (APICM). This projectile contains antipersonnel grenades (the number varies depending on the caliber of the weapon) which are extremely effective on antipersonnel targets. Antipersonnel improved conventional munitions (APICM) is available for 105-mm and 155-mm howitzers. The APICM (see figure 3-19) are most effective against unwarned, exposed personnel. When the fuze functions, an expelling charge forces the grenades out through the base of the projectile. Small vanes on each grenade flip upward, arming the grenade and stabilizing it in flight. When the striker plate on the base of the grenade contacts the ground, the grenade is hurled upward four to six feet and detonates. M449 APICM dispersion pattern is generally elliptical in shape. The dispersion pattern covers approximately 100 meters by 60 meters. APICM is no longer manufactured but is still held in war reserve. 155-mm Figure 3-19. APICM grenades. DUAL-PURPOSE IMPROVED CONVENTIONAL MUNITIONS 3-111. Dual-Purpose Improved Conventional Munitions (DPICM). This projectile contains antipersonnel and anti-material grenades (see figure 3-20 on page 3-32). This projectile was designed for use against equipment, lightly armored vehicles, and personnel. Dual-purpose improved conventional munitions (DPICM) is available for both the 105-mm and 155-mm howitzer. Dual-purpose improved conventional munitions are base-ejection, payload-carrying projectiles. These projectiles are fired with base ejecting time fuzes and are filled with dual-purpose grenades. During flight, the base of the projectile is blown off and centrifugal force disperses the grenades radically from the projectile line of flight. After the grenade is ejected, a ribbon streamer arms and stabilizes it. On impact, a shaped charge that can pierce light armor is detonated. The surrounding steel case fragments are very effective against personnel as well. DPICM dispersion generally changes shape from elliptical at minimum ranges and lower charges to almost circular at maximum ranges. At minimum ranges, the dimensions are approximately 50 meters by 100 meters. At maximum ranges, they are approximately 100 meters by 120 meters. 13 April 2016 TC 3-09.81 3-31 Chapter 3 Figure 3-20. 155-mm DPICM grenade. 3-112. Table 3-5 describes the various improved conventional munition projectiles. Table 3-5. Improved Conventional Munitions Weapon Projectile Number of Grenades Antipersonnel ICM 155-mm (Figure 3-19) M449 60 Dual-purpose ICM 155-mm (Figure 3-20) M483A1 88 155-mm M864 72 105-mm M915 42 MLRS M26 Rocket 644 M77 MLRS ER MLRS 518 XM85 MLRS GMLRS 400+ XM85 Legend: ER—extended range GMLRS—guided multiple launch rocket system ICM—improved conventional munition mm—millimeter MLRS—multiple launch rocket system BASE BURN ROUND 3-113. Base Burn. Some munitions incorporate base burn (also known as Based Bleed) technology to increase its range. Base burn technology was developed to reduce the amount of base drag on a projectile, thereby increasing the achieved range. The drag is reduced by a (base) burner unit located on the base of the projectile. Once ignited, the base burner unit bleeds hot gas which causes the flow of air at the base to be less turbulent. The decrease in turbulence causes less base drag. (Base drag accounts for about 50 percent of total drag.) The amount of thrust produced by the base burner unit is negligible and does not serve the same function as the rocket motor on RAP. 3-114. The M864 base burn DPICM has a larger dispersion pattern than that of the M438A1 DPICM despite having fewer grenades. However, because it is designed for employment at longer ranges, which produces a steep angle of fall, the dispersion pattern is typically circular. At its designed ranges, the dispersion pattern covers approximately 150 meters by 150 meters. The projectile will not be used for training; all assets will become war reserve. Data may be computed manually by using FT 155-AU-PAD and FT 155-ADD-U-PAD. 3-32 TC 3-09.81 13 April 2016 Ballistics FAMILY OF SCATTERABLE MINES 3-115. Family of Scatterable Mines (FASCAM). There are two types of artillery delivered mines: Area Denial Artillery Munition (ADAM) and Remote Anti-Amor Mine (RAAMS). The ADAM was developed for use against personnel targets, to deny terrain, and to block avenues of approach. RAAMS was developed for use against armored targets. Both the ADAM and RAAMS have preset self-destruct times of either short (within 4 hours) or long (within 48 hours). FASCAM is available for the 155-mm howitzer only. The family of scatterable mines adds new dimension to mine warfare, providing the maneuver commander with a rapid, flexible means of delaying, harassing, paralyzing, canalizing, or wearing down the enemy forces in both offensive and defensive operations. Mines can force the enemy into kill zones, change their direction of attack, spend time in clearing operations, or take evasive actions. FASCAM presents an array of air and FA-delivered scatterable mines available to maneuver force commanders. The two types of FA-delivered scatterable mines are ADAM and RAAMS. RAAMS Projectiles 3-116. Use RAAMS projectiles to delay or disrupt threat formations and maneuver or to reinforce existing obstacles. A 155-mm howitzer fires the RAAMS projectile which base ejects anti-armor mines (see figure 3-21) over the target area. After a short delay to allow for mine freefall, impact, and roll, the magnetically fuzed mines arm themselves. Any metallic object such as a tank or self-propelled vehicle passing over the mines will cause the mines to detonate. Random mines have anti-disturbance features that cause the mines to detonate if they are moved or picked up. If not detonated, RAAMS mines begin to self destruct (SD) after 80 percent of the factory set SD time elapses. The probability of a live mine existing past its stated SD time is 0.001. Upon arming field artillery delivered scatterable mines perform a self test. All mines that fail the self test SD immediately. The SD time for the munitions are:  The M718 and M718A1 projectiles have a long SD time (48 hours).  The M741 and M741A1 projectiles have a short SD time (4 hours). Note. The United States is aligning its anti-personnel landmines (APL) policy outside the Korean Peninsula with the key requirements of the Ottawa Convention, the international treaty prohibiting the use, stockpiling, production, and transfer of APL, which more than 160 countries have joined, including all of our North Atlantic Treaty Organization (NATO) Allies. This means that the US will not employ the ADAM-S and ADAM-L projectiles outside the Korean Peninsula Most RAAMS (and ADAM) mines arm in two minutes. Product improved mines (type designated A1 arm in 45 seconds). Figure 3-21. RAAMS mine. 3-117. Use ADAM mines against personnel, dismounted personnel in an armored attack, or on existing antitank obstacles to hinder dismounted breaching. When employed against a threat that has a dismounted breaching capability, deliver ADAM mines directly on top of a RAAMS minefield. ADAM rounds are always the last rounds fired when used in conjunction with RAAMS or other munitions. This prevents the accidental destruction of the ADAM munitions by other munitions. 3-118. A 155-mm howitzer fires the ADAM projectile which base ejects 36 antipersonnel mines (see figure 3-22 on page 3-34) over the target area. When an ADAM mine comes to rest on the ground, several 13 April 2016 TC 3-09.81 3-33 Chapter 3 tripwire sensors are deployed out to a maximum distance of 20 feet. When a sensor is disturbed or tripped, it propels a small ball like munitions two to eight feet upward. The munition detonates and scatters approximately 600 1.5 grain steel fragments in all directions. If not detonated, the ADAM mines will begin to SD after 80 percent of the factory set SD time elapses. The destruct times for the munitions are:  The M692 projectile has a long SD time (48 hours).  The M731 projectile has a short SD time (4 hours). Figure 3-22. ADAM mine. SENSE AND DESTROY ARMOR (SADARM M898) 3-119. The M898 Sense and Destroy Armor (SADARM) projectile is a base ejecting munition carrying a payload of two target sensing sub-munitions. The projectile is a member of the M795 family. The technical fire direction computations are similar to those used for the ADAM projectile, in that low level wind corrections must be applied to the firing solution (because of the high Height of Burst) in order to place the payload at the optimal location over the target area. SADARM is no longer manufactured but is still held in war reserve EXCALIBUR 3-120. The M982 Excalibur is a family of 155-mm fire and forgets global positioning system (GPS)/internal measurement unit guided projectiles that use a jam resistant GPS receiver and a guidance package that enables the projectile to fly with GPS accuracy to preprogrammed aim-points independent of range. The M982 projectile uses a gliding airframe to achieve extended range. The M982 employs a nonballistic flight path, which reduces the ability of counter-battery radars to accurately locate the firing unit and enhances friendly force survivability. Excalibur delivers a high explosive warhead out to ranges between 8 and 37.5 kilometers. Excalibur has three fuze options: point detonating, delay and proximity with a height of burst (HOB) of 3.7 meters. 3-121. Excalibur is only fired at high angle fire. This allows maximum acquisition time for the GPS receivers and guidance components, and for corrections along the guided portion of the trajectory. High angle fire optimizes the ranges Excalibur can achieve, due in large part to the projectile’s aerodynamic design and features that allow the projectile to “glide”, thus achieving greater range than a purely ballistic trajectory projectile. The Excalibur’s guidance system corrects its flight path for optimum attack angle and precision attack on the target. 3-122. Once near the target location, Excalibur performs a top down maneuver that allows for a nearly vertical attack angle on the target. Excalibur does not require laser designation and cannot be guided onto the target by a laser. It is not designed to destroy buildings or as a tank killer. The Excalibur projectile has roughly the equivalent explosive power of a standard M107 artillery projectile. The unitary warhead has a hardened casing that enables it to penetrate 4” of reinforced concrete before detonating (fuze delay). 3-34 TC 3-09.81 13 April 2016 Ballistics PRECISION GUIDANCE KIT (PGK) 3-123. The Precision Guidance Kit (PGK) is comprised of the M1156 multioption fuze. The PGK is a low cost fuze alternative designed to increase effectiveness by ensuring rounds impact at or near the input target coordinates and are within the lethal radius of the round. This achieves increased efficiency with fewer rounds needed to achieve desired results. The PGK enhances accuracy of M549A1 or M795 155-mm artillery projectiles with the aid of global positioning system acquisition and guidance. This fuze allows for closer support of friendly forces and reduces the overall logistics burden by providing a near-precision capability to M549A1 or M795 high explosive cannon artillery projectiles. For more information on the PGK, see TB 9-1390-226-13. 13 April 2016 TC 3-09.81 3-35 This page intentionally left blank. Chapter 4 Muzzle Velocity Management Two howitzers of the same caliber, firing the same ammunition, charge and elevation, will seldom deliver fire at exactly the same range. The achieved muzzle velocity is the result of forces acting on the projectile within the cannon tube. To obtain accurate artillery fire, the performance of the weapon projectile family-propellant lot-charge combination must be known. If it is not known, the result can be reduced effects on the target or friendly casualties (for example, danger close, final protective fire [FPF], converged sheafs, and so on). Firing tables provide standard muzzle velocities for a standard weapon firing standard ammunition under standard conditions. However, muzzle velocities achieved in actual firing may differ from the standard muzzle velocities because of variations in the manufacture of the weapon and ammunition, wear in the weapon tube, projectile weight, propellant temperature, propellant lot efficiency, or a combination of these factors. The Muzzle Velocity System (MVS) enables a firing unit to continually update muzzle velocity data. This chapter describes muzzle velocity management with the MVS as well as predictive techniques. SECTION I: MUZZLE VELOCITY TERMS 4-1. Muzzle velocity (MV)-the velocity achieved by a projectile as it leaves the muzzle of the weapon (measured in 0.1 meters per second). 4-2. Standard muzzle velocity-An established muzzle velocity used for comparison. It is dependent upon the weapon system, propellant type, charge, and projectile family. It is also referred to as reference muzzle velocity. Standard muzzle velocities can be referenced in the Tabular Firing Tables. 4-3. Muzzle velocity variation (MVV)-the change in muzzle velocity of a weapon (expressed in ±0.1 meters per second) from the standard muzzle velocity or arbitrary selected standard. 4-4. Projectile family-a group of projectiles that have exact or very similar ballistic characteristics. Within the projectile family the projectiles' external shape, mass, center of gravity, moment of inertia, and surface finish are similar. If we were to fire an infinite number of rounds, their mean point of impact would be within 1 PER and PED of the mean point of impact of the family head projectile. 4-5. Propellant type-the nomenclature of the propellant used for a particular charge. 4-6. Charge group-the charges within each propellant type associated with a projectile family, within which MVVs can be determined. (See table 4-1 on page 4-4). This has been referred to as propellant model or powder model in the past and in other references. In separate-loading ammunition (155-mm) these terms are synonymous, but in semi-fixed ammunition (105-mm), three charge groups are within a propellant type. Charge groups may change depending on the projectile family. 4-7. Preferred charges-the charges preferred for measuring and transferring muzzle velocities. These charges produce consistent predictable muzzle velocities. The MVVs they produce should not vary more than (±1.5 meters per second for the same charge or other charges of the same charge group. Therefore, the MVV determined for one charge of a propellant type will be similar (±1.5 m/s) to another charge of the same propellant type and lot. Preferred charges are identified in table 4-1 (on page 4-4). 4-8. Restricted charges-those charges within a charge group to which it is not preferred to transfer measured MVVs or for which it is not authorized to fire (is based on the weapon Technical Manual [TM]). 13 April 2016 TC 3-09.81 4-1 Chapter 4 The performance of a restricted charge is not indicative of the performance of other charges within the charge group. 4-9. Adjacent charge-charges within a charge group which are one charge increment greater or less than the charge calibrated. Used in the conduct of a calibration and subsequent lot inference techniques. 4-10. Propellant lot-a group of propellants made by the same manufacturer at the same location with the same ingredients. 4-11. Calibration -is the process of measuring the muzzle velocity of a weapon and then performing a comparison between the muzzle velocity achieved by a given howitzer and the accepted standard. There are two types of calibration--absolute and comparative (see figure 4-1).  In absolute calibration, the weapon’s achieved muzzle velocity is compared to the firing table reference muzzle velocity (also known as Standard Muzzle Velocity).  In a comparative calibration, the achieved muzzle velocities of two or more weapons are compared to an arbitrarily selected standard from the performance of a group of weapons being calibrated together. Figure 4-1. Comparative and Absolute Calibration results. 4-12. Inferred calibration- the MV of a weapon is determined through mathematical procedures by using data from a first lot calibration (baseline data) and the relative efficiency of a second lot of propellant. 4-13. Muzzle Velocity System (MVS) - The MVS is a MV measurement system, which operates on the Doppler principle. The system is based on an X-band transceiver and a MV processor. The purpose of the MVS is to provide an accurate MV reading for a projectile fired from the howitzer. This information can be used to provide a reasonable estimate of the average MV for rounds to be fired for a new fire mission; thereby improving the possibility of first round effects on the target. It is used to measure the speed of the projectile as it leaves the muzzle of a weapon. It can determine MVVs. Additionally the MVS can apply corrections for non-standard conditions and determine a calibrated MVV.  Paladin Digital Fire Control System (PDFCS) Muzzle Velocity System (MVS). This is a replacement for the M90 Velocimeter. It is used on the Paladin weapon system and is an integrated component of the PDFCS. This system was formally known as the M93. See Appendix K of the ATP 3-09.70  The M94 is a MVS used in towed M119A2/A3 (105mm) and M777A2 howitzers. For more information see TM 9-1290-364-14&P. Note: USMC unit use the Muzzle Velocity Sensor System (MVSS). 4-14. Muzzle Velocity System (MVS) Readout average- is the average MV measured by the MVS which has not been corrected for standard projectile square weight and standard propellant temperature. 4-2 TC 3-09.81 13 April 2016 Muzzle Velocity Management 4-15. Calibrated muzzle velocity- is an MVS readout average that has been corrected to standard projectile square weight and propellant temperature. MVV= Calibrated MV- Standard MV. 4-16. Historical muzzle velocity- is a calibrated muzzle velocity which has been recorded in a muzzle velocity logbook. 4-17. Erosion- is the wear in a howitzer tube that is the result of firing rounds. It is measured from a pullover gauge reading (POG), which is described in inches, or estimated by computing the equivalent full charges (EFC) for erosion. This is determined by multiplying the number of rounds fired with a given charge and the number of EFCs per round for that charge and projectile. The table used to compute EFC’s is found in the introduction of the Tabular Firing Table (TFT) 4-18. Shooting strength-is the reduction in the achieved muzzle velocity of a howitzer overtime caused by erosion, which is a function of erosion and projectile family ballistics. 4-19. Ammunition efficiency- is the change in velocity which is the sum of the projectile efficiency and propellant efficiency. 4-20. Projectile efficiency- is the known deviations from the standard for a particular projectile which affect the achieved velocity. For example, a high-explosive (HE) Ml07 projectile which weighs 3◙ (93.9 pounds), vice the standard 4◙ (95.0 pounds), would have a predictable change in velocity, depending on the charge fired. 4-21. Propellant efficiency-is the known deviations from the standard for a particular propellant which affect the velocity of the projectile. For example, a lot of M232A1 propellant may perform differently than the standard for that propellant type but is still acceptable for firing. 13 April 2016 TC 3-09.81 4-3 Chapter 4 Table 4-1. Projectile Families, Propellant Types, and Charge Groups. PROJECTILE CHARGE PREFERRED FAMILY PROPELLANT GROUPS CHARGES 105 MM HE (M1) M67 1-2 1-2 3-5 3-5 6-7 6-7 DPICM (M915) M200 Single Increment (8) Single Increment (8) RAP (M927) M67 7 7 RAP (M548) M176 3-5 3-5 6-7 6-7 RAP (M913) M229 Single Increment (8) Single Increment (8) 155 MM HE (M107) M3A1 2-5 3-5 M231 1-2 N/A M4A2 3-7 5-7 M232/A1 3-4 4 M119A1 8 8 M119A2 7 7 HE (M795) M3A1 3-5 3-5 M231 1-2 N/A M4A2 4-7 5-7 M232/A1 3-5 4 M119A1 8 8 M119A2 7 7 M203A1 8 8 RAP (M549) M4A2 7 7 M232/A1 3-5 4 M119A1 8 8 M119A2 7 7 M203A1 8S 8S DPICM (M864) M4A2 7 7 M232/A1 3-5 4 M119A1 8 8 M119A2 7 7 M203A1 8S 8S EXCALIBUR (M982) M232/A1 3-4 4 EXCALIBUR M232/A1 3-4 4 (M982A1) Legend: HE = High Explosive DPICM = Dual-Purpose Improved Conventional Munition MM – millimeter RAP = Rocket Assisted Projectile SECTION II: CORRECTION TABLES AND FORMS MUZZLE VELOCITY CORRECTION TABLES (MVCT) 4-22. The Muzzle Velocity Correction Tables (MVCT) are published for the information and guidance of personnel whose responsibility is the use of data generated by the MVS. The correction tables contain data to correct the readout average to what it would have been if the reading had been determined with a standard square-weight projectile and a standard propellant temperature. The information in the tables was 4-4 TC 3-09.81 13 April 2016 Muzzle Velocity Management compiled from Fire Control Inputs (FCI’s) maintained by the Firing Tables and Ballistics Division (FTaB). Fire control is all operations connected with the planning, preparation, and actual application of fire on a target. 4-23. The muzzle velocity readout from a MVS is the projectile velocity at the muzzle for the projectile weight and propellant temperature at the time of firing. This muzzle velocity must be corrected to the muzzle velocity that would have been read for standard projectile weight and propellant temperature. The MVS tables contain muzzle velocity corrections due to nonstandard projectile weight and propellant temperature for weapon, projectile and propelling charge combinations. 4-24. Parts of the MVCT include:  Cover  Table of contents.  Introduction.  Muzzle Velocity Correction Tables  Section Cover Sheet (See figure 4-2 on page 4-6) The Section cover of the MVCT provides information concerning the weapon system(s) and projectile(s) to which data in the section apply. Several projectiles may be listed on the cover if they are within the same projectile family because of ballistic similarity. Also provide fuze weight corrections. Note: The MVCT-2 is used as the example throughout this section. Figure 4-2 (on page 4-6) shows a portion of the Section 5 cover found on page 33 of the MVCT-2 Note: The calibrated muzzle velocity is the summation of the average muzzle velocity readout and corrections due to the nonstandard projectile square weight and propellant temperature (derived using interpolation if necessary). Corrections for any difference in fuze weight must also be incorporated. The table located at the bottom of the section cover must be used with the proper projectile/fuze combinations. Before entering the correction table, projectile square weight must be adjusted for differences in fuze weight as indicated by the table. To find the corrections for adjusted projectile square weight with a ½ square increment, interpolate between the corrections for the higher and lower values Note: The Standard muzzle velocities are based on the M557 fuze. However, some Tabular Firing Tables (TFT) are based on the M739A1 fuze. Therefore, the standard muzzle velocities in those TFT were adjusted for the fuzed projectile weight.  Standard Muzzle Velocity- after the Section Cover the MVCT lists the standard muzzle velocities. This standard MV could also be found in the appropriated TFT (See figure 4-2 on page 4-6). 13 April 2016 TC 3-09.81 4-5 Chapter 4 Figure 4-2. Section Cover and Standard MV Example.  Correction Tables. The correction tables are separated by Weapon System, Projectile Family, Propellant Model, and Charge. In the muzzle velocity correction table, the projectile weight and propellant temperature are expressed to 1 square, 10° Fahrenheit and 5.6° Celsius respectively. In general, plus signs are omitted from these tables. Therefore, numbers without signs are to be considered positive. To determine correction factor enter MVCT for the appropriate weapon system and projectile family. Locate the page containing the table for the same charge fired in the calibration. Enter the table with the average propellant temperature and the weight of the projectile fired (ensure that fuze correction is applied if required). Interpolate to the nearest ± 0.1 m/s (See figure 4-3 on page 4-7) to determine the value to correct the readout average to standard. Note: When temperatures are greater than 130° use the last listed value 4-6 TC 3-09.81 13 April 2016 Muzzle Velocity Management Figure 4-3. Correction Table Charge 4H M232A1, for M107 Projectile Family. DA FORM 4982-1 M90 VELOCIMETER WORK SHEET 4-25. DA Form 4982-1 M90 Velocimeter Work Sheet (figure 4-4 on page 4-8) is used to determine the calibrated muzzle velocity by correcting for variations in projectile square weight and propellant temperature from the standard. It is divided into four major sections. These sections are  Administrative information. In this section the projectile family-propellant lot charge combination is recorded.  Calibration Data. In this section the howitzer(s) tube and temperature information at the time of firing is recorded.  Muzzle Velocity System Readout. In this section the readout and average values are recorded.  Muzzle Velocity Computations. In this section corrections determined form the MVCT are recorded and applied by the algebraic sum of the readout average and the correction factor. Also there is a remark portion in which computations could be recorded as necessary. 13 April 2016 TC 3-09.81 4-7 Chapter 4 Figure 4-4. M90 Velocimeter Work Sheet. DA FORM 4982 MUZZLE VELOCITY RECORD 4-26. DA Form 4982 Muzzle Velocity Record (figure 4-5) is the record of a calibration kept in the battery or platoon muzzle velocity log book. The top part of the form (FIRST-LOT CALIBRATION) is used to 4-8 TC 3-09.81 13 April 2016 Muzzle Velocity Management determine the weapon MVV for a specific charge, when corrected to standard. The lower part of the form (SECOND-LOT CALIBRATION AND SECOND-LOT INFERENCE) is used to infer muzzle velocity data for a second lot of propellant and/or ammunition. Figure 4-5. Muzzle Velocity Record. 13 April 2016 TC 3-09.81 4-9 Chapter 4 SECTION III: TECHNIQUES TO DETERMINE MUZZLE VELOCITY VARIATIONS 4-27. Three techniques can be used to determine muzzle velocity variations within the firing unit. The accuracy and complexity of these different techniques varies greatly. Each of the techniques must be understood and applied correctly to the tactical situation. The following order of preference can be used as a guideline. The techniques are listed in order of decreasing preference.  First Lot Calibration (baseline calibration).  Subsequent lot inferred calibration.  Predictive muzzle velocity techniques. Note: Muzzle Velocities achieved in actual firing differ from the standard muzzle velocities as a result FDC should not assume standard muzzle velocity FIRST LOT CALIBRATION (BASELINE CALIBRATION). DETERMINATION OF CALIBRATED MUZZLE VELOCITY DA FORM 4982-1 4-28. Determine calibration data. The howitzer section provides admin information and MVS readout values to the FDC. Normally, data from six usable rounds, all preferably fired within 20 minutes, are used to ensure the most accurate calibration data. These six rounds can be from any fire mission conducted by the firing unit. Specially conducted calibration missions are not required. If the howitzer tube is cold (that is, has not been engaged in firing or in low air temperatures) the firing of warm-up rounds is recommended. Fewer than six rounds can be used. In these situations, the calibration validity is reduced in the same way that the validity of a registration is reduced when the number of rounds fired is less than normal. In these situations, refer to Chapter 10, Table 10-1 for validity information and the effect of reduced rounds on the calibration data. Powder temperature differences between rounds decrease the validity of the calibration. To reduce powder temperature changes from round to round, use proper propellant handling and storing procedures in the firing unit and fire all rounds measured for a calibration within a 20-minute period. Follow these procedures in the calibration of all weapons. The FDC will collect the MVS readout values and calibrated MV from the section chiefs and record the values on DA Form 4982. FDC will also collect the MVS determined MVV and record it on DA Form 4982 for all weapons. The FDO is responsible to verify/validate the data received by the section chief. Note: The MVS can determine MVV and apply corrections for non-standard conditions to determine calibrated MV. The step mentioned in this section can be used to verify/validate MVS data 4-29. Determine MVS readout average. The FDO inspects the readout values for all rounds and deletes any invalid readout values, those exceeding the readout average by ±3.0 m/s. This ±3.0 m/s approximates 4 PER in the target area for the given charge. The FDC personnel then determine the new readout average for the usable rounds by adding all usable readout values and dividing the sum by the number of usable rounds. This value includes the effects of non-standard propellant temperature and projectile weight. 4-30. Determination of calibrated MV. The MVS readout average is not used in its original form because it includes the effects of projectile weight and propellant temperature on the muzzle velocity. The MV can be used when the corrections for projectile weight and propellant temperature are applied by extracting the value from the appropriate table in the MVCT manual and applying that value to the readout average. The result is the calibrated muzzle velocity for the weapon. 4-31. Complete MVS worksheet. Once the velocity of the rounds fired has been determined, FDC personnel are responsible for verifying and completing the DA Form 4982-l and place into the unit muzzle velocity logbook. 4-10 TC 3-09.81 13 April 2016 Muzzle Velocity Management COMPLETE THE MUZZLE VELOCITY RECORD (DA FORM 4982). 4-32. DA Form 4982 is the record of a calibration kept in the battery or platoon muzzle velocity log book. For future reference, place the completed muzzle velocity record into the unit muzzle velocity logbook under the appropriate weapon projectile family-propellant type-charge group. 4-33. The determined MVV is used in the solution of concurrent met technique and subsequent met application and terrain gun position corrections. The lower part of the form (SECOND-LOT CALIBRATION AND SECOND-LOT INFERENCE) is used to infer muzzle velocity data for a second lot of propellant and/or ammunition. SUBSEQUENT LOT INFERRED CALIBRATION. 4-34. Inferred subsequent lot calibration techniques allow a firing unit to quickly update muzzle velocity information for a given projectile family-propellant lot combination, when firing a new lot of propellant. Subsequent lot calibration is used to isolate the difference in efficiency between two propellant lots for one howitzer firing the same projectile family. This difference is applied to the first lot calibration data for the other howitzers to determine calibration data for the second lot. This technique can be used when the situation does not permit the calibration of the new lot with all guns. 4-35. To accomplish this technique, the following requirements must be met:  Calibration of the first lot must be completed for the entire unit.  Calibration of a second lot must be completed for one gun.  Subsequent lot should be calibrated with the same or adjacent charge. 4-36. A calibration should be completed with all howitzers as soon as the situation allows. PREDICTIVE MUZZLE VELOCITY TECHNIQUE. 4-37. While it is not practical to predict (within ±0.1 m/s) the velocity of every round, it is possible to approximate velocities to within ±1 or ±2 m/s with current available information. This may be useful when calibration is not possible, when updating calibration data, or when trying to increase the accuracy of inferred MV techniques. 4-38. When calibration is not possible, the shooting strength of the howitzer can be used as the MVV. While this may be enough when no other data are available, it is important to understand that an MVV consists of more than just shooting strength. An equation can be created for determining an MVV by using its basic parts. MVV= SHOOTING STRENGTH + AMMUNITION EFFICIENCY + ROUND TO ROUND VARIATION 4-39. If all three elements are known, it is possible to determine a value for MVV. It is neither practical nor necessary to quantify round-to-round variation. This element is usually small and subject to rapid change. Projectile efficiency, as a part of ammunition efficiency, is accounted for in solving the concurrent and subsequent met techniques. Therefore, if the round-to-round variation and the projectile efficiency are eliminated from the equation, the howitzer shooting strength and the propellant efficiency of the propellant lot to be fired can approximate the MVV. MVV= SHOOTING STRENGTH + PROPELLANT EFFICIENCY 4-40. If calibration is not possible, adding the propellant efficiency to the shooting strength will result in a more accurate MVV for determining firing data than if the shooting strength is considered alone. This MVV can be used as the MVV for manual fire missions. Each howitzer has a value for shooting strength for each projectile family. Also, the value of propellant efficiency applies to any projectile family with which the propellant lot is fired. 13 April 2016 TC 3-09.81 4-11 Chapter 4 ESTIMATING SHOOTING STRENGTH 4-41. There may be times when calibration is not possible. If the MVS is not available or there is not time to conduct a calibration, it may be necessary to determine the shooting strength of the howitzer by other means. The shooting strength of a howitzer can be determined by using pullover gauge readings (POG) and/or erosion EFC service round effects with the appropriate TFT for the weapon-projectile-propelling charge combination to be fired. DA Form 2408-4, Weapon Record Data, provides the information to determine the shooting strength of each howitzer. (See figure 4-6.) Figure 4-6. Digital Weapon Record Data. 4-42. The shooting strength is obtained by determining the most recent pullover gauge (POG) reading from the weapon's DA Form 2408-4 (E) (Weapon Record Data or The Gun Book) and converting that to a loss in Muzzle Velocity by entering the appropriate TFT for the weapon system and projectile family. (Ensure you use the appropriate TFT for your weapon system and projectile family). If the howitzer has fired since the last POG reading, you must first convert the POG reading to effective full charges (EFCs) and then add the EFCs for those rounds fired since the last POG reading before converting that total number of predicted EFCs to a predicted loss in Muzzle Velocity (Note: Shooting Strength will always be negative) 4-43. The number of EFCs for those rounds fired since the last POG is determined by multiplying the number of rounds fired for a specific projectile and propellant by the equivalent erosion effect in decimals for the charge fired listed in the introduction of the TFT. Different projectile families have different TFTs and consequently different values for equivalent erosion effect in decimals. 4-44. Pullover gauge readings can be determined regularly by the maintenance section in conjunction with borescoping the howitzer. The most accurate technique is to combine the pullover gauge reading and the erosion EFCs fired after the pullover gauge reading to determine an expected loss in muzzle velocity. The most recent pullover gauge reading or total erosion EFCs may be used to determine the approximate loss in muzzle velocity. PROPELLANT EFFICIENCIES. 4-45. Propellant efficiency (PE) is known deviations from the standard for a particular propellant which affect the velocity of the projectile. The propellant efficiency information (see example in figure 4-7 on page 4-13) contains data useable with predictive muzzle velocity techniques. The information is a result of the initial acceptance test of the specific propellant lot fired at the time the entire lot of propellant was purchased by the government. The first two numbers (i.e. 03 in IOP09M-031030) generally indicate the 4-12 TC 3-09.81 13 April 2016 Muzzle Velocity Management year the propellant lot was produced. Some lots are quite old and storage location and conditions over time may have reduced the accuracy of the propellant efficiency as a predictive measure. Nonetheless, the propellant efficiencies are a valuable tool to the FDO in improving the accuracy of his unit when calibration information is not yet available for a particular propellant lot. This information is not intended to be a substitute for calibrating a "new" lot of propellant that your unit receives, rather it should be used only until you can calibrate one gun with the "new" lot and eventually establish a baseline with that lot as time and the tactical situation permit. (This is in accordance with the order of preference for calibration or muzzle velocity variation information). Propellant efficiencies will prove extremely valuable in a situation where you receive a new lot of propellant that you have not previously calibrated your howitzers with. In this situation, if you will not have the opportunity to calibrate the new lot prior to firing for its intended use, you should use the column labeled "Propellant Efficiency", with the charge closest to the one you will fire, and apply it in the following equation: MUZZLE VELOCITY VARIATION = SHOOTING STRENGTH + PROPELLANT EFFICIENCY MVV= SS + PE Figure 4-7. MACS Propellant Efficiencies (PE) Example. Note: DO NOT USE Figure 4-7 to predict MVV’s for firing. 13 April 2016 TC 3-09.81 4-13 Chapter 4 SECTION IV: EXAMPLES OF THE TECHNIQUES USED TO DETERMINE MUZZLE VELOCITY COMPLETE M90 VELOCIMETER WORKSHEET (DA FORM 4982-1) 4-46. Complete M90 Velocimeter worksheet. Step Action Drill for DA Form 4982-1. This will include the steps in table 4-2 on page 4-14. A completed DA Form 4982-1 is shown in figure 4-8 on page 4-15. STEP Table 4-2. Steps for Completing DA Form 4982-1. ACTION 1 Verify the admin data. 2 Verify the weapon bumper number. 3 Verify the weapon tube number. 4 Verify the starting powder temperature for each howitzer. 5 Verify the ending powder temperature for each howitzer. 6 Determine and record the average powder temperature for each howitzer to the nearest degree. 7 Verify the MVS readout by round for each howitzer. 8 Average all the usable measured muzzle velocities for each howitzer. 9 Compare the average of the usable measured muzzle velocities with each measured muzzle velocity for each howitzer. 10 If any measured muzzle velocity is more than ±3.0 m/s from the average, discard it. Discarding more than one velocity at a time may be necessary. 11 If any muzzle velocities were discarded, repeat steps 8 through 10 above. If no further rounds are discarded, this is the readout average. 12 Record the readout average for each howitzer. 13 Locate the portion of the MVCT for the weapon system fired. 14 Locate the portion of the MVCT for the projectile family of the projectile fired. 15 Locate the page of the MVCT for the charge of the propellant type used. 16 Find the projectile ◙ weight across the top of the table. Note: To find the corrections for adjusted projectile square weight with a ½ square increment due to fuze correction, interpolate between the corrections for the higher and lower values (for an example see Table 4-3 on page 4-16) 17 Find the average powder temperature on the left or right edge of the table. 18 Find where the projectile weight and the powder temperature intersect in the table. This is the correction for the nonstandard condition(s). Note: If the average powder temperature is not listed but is within the temperatures listed, interpolation is required. If it is not within the temperatures listed, then use the last listed value (that is, -40° or +130°F). 19 Determine and record the calibrated muzzle velocity by algebraically applying the correction determined in step 18 to the readout average from step 12. Legend: F – farenheit m/s – meters per second MVCT – muzzle velocity coreection tables MVS – muzzle velocity system 4-14 TC 3-09.81 13 April 2016 Muzzle Velocity Management Figure 4-8. M90 Velocimeter Worksheet Example. 4-47. Table 4-3 (on page 4-16) explains the process to account for the projectile half-square weight when it is other than standard. 13 April 2016 TC 3-09.81 4-15 Chapter 4 Table 4-3. Example Determining ½◙ Correcting for Fuze. STEP 1 2 3 ACTION Identify the Known Data: Howitzer M109A6 Bumper # A25 Projectile M107 Propellant Charge M232A1, 4H Projectile Weight 5 SQ Average Propellant Temperature 62° F Average Muzzle Velocity Readout 699.9 m/s Fuze M782 Fuze Correction: Before entering the muzzle velocity correction tables, the projectile weight must also be corrected for any differences in fuze weight. From the known data above: M782 fuze → - ½◙ (fuze table page 33 MVCT-2 See Figure 4-2) (5◙-½◙= 4½◙) 4½◙ Interpolation Technique: Interpolate between 4◙ and 5◙ to determine the ½◙ correction factors for the listed values (page 57 MVCT-2 See Figure 4-3)and interpolate as follows: 3a ½ Square Weight Correction for 60° F 4◙ 0 m/s 4½◙ ? m/s 5◙ 4.1 m/s ½ Square Weight Correction for 70° F 4◙ 0 m/s 4½◙ ? m/s 5◙ 2.4 m/s 3b Temperature Correction for 4½◙ 60° F +2.9 m/s 62° F ? m/s 70° F +1.2 m/s Muzzle Velocity Correction = +2.6 m/s 4 Determine Calibrated MV. Calibrated MV= MEASURE MV + CORRECTIONS 699.9m/s + (+2.6m/s) Calibrated MV= 702.5 m/s 4-16 TC 3-09.81 13 April 2016 Muzzle Velocity Management COMPLETE THE MUZZLE VELOCITY RECORD (DA FORM 4982) 4-48. Complete the Muzzle Velocity Record (DA form 4982). Table 4-4 provides the steps for completing DA Form 4982, and figure 4-9 shows the potion of the form completed through the first nine steps. Table 4-4. Completing DA Form 4982 for a First-Lot Calibration. STEP Reference ACTION 1 DATE and POWDER MODEL blocks. Record date and powder model in the appropriate blocks in the upper right comer of the form. 2 SHELL/FAMILY block. Record the projectile model and family. 3 FIRST POWDER LOT NUMBER block. 4 GUN NUMBER/CHARGE FIRED block. Record the manufacturer's number that identifies this particular lot of powder. Record the particular charge increment fired next to the appropriate weapon number. 5 WEAPON BUMPER NUMBER block Record the weapon bumper number. (Line 1). 6 WEAPON TUBE NUMBER block (Line 2). Record the serial number of the tube. 7 FIRST-LOT CHARGE STANDARD From the TFT, extract the standard MV for the charge fired MUZZLE VELOCITY block (Line 3). in the calibration. 8 CALIBRATED MUZZLE VELOCITY Record the calibrated muzzle velocity from line 7 of the block (Line 4). MVS work sheet. 9 FIRST-LOT PIECE MUZZLE VELOCITY VARIATION (Line 5). Compare the calibrated MV to the standard MV, and record the MVV (line 4 - line 3 = MVV). Legend: MV – muzzle velocity MVS – muzzle velocity system MVV – muzzle velocity variation TFT – tabular firing tables Figure 4-9. DA Form 4982 Muzzle Velocity Record for a first lot calibration. 13 April 2016 TC 3-09.81 4-17 Chapter 4 SUBSEQUENT LOT INFERRED CALIBRATION 4-49. Subsequent Lot Inferred Calibration. Table 4-5 provides the steps for conducting a subsequent lot calibration. Figure 4-10 (on page 4-19) shows DA Form 4982-1 completed for a second-lot inferred calibration. Figure 4-11 on page 4-20 shows DA Form 4982 completed for a second-lot inferred calibration. Table 4-5. Completing DA Form 4982 for Subsequent Lot Calibration. STEP Reference ACTION 1 Calibration, first lot. Conduct a calibration for all howitzers for the first lot of propellant. Complete DA Form 4982-1 in accordance with Table 4-2 (on page 4-14). 2 Calibration, second lot. Conduct a calibration for one howitzer for the second lot of propellant. Complete DA Form 4982-1 in accordance with Table 4-2 (on page 4-14). 3 Administrative information Record the admin information on DA Form 4982, to include the date, powder model, shell/family, and first powder lot number. 4 FIRST-LOT CALIBRATION section Record the data from the first calibration for each howitzer on lines 1 through 5 from the first DA Form 4982 (Figure 4-9 on page 4-17). 5 SECOND-LOT CALIBRATION section Enter the date, time, and powder lot number. 6 SHELL/FAMILY block Enter the projectile model and family 7 SECOND-LOT POWDER GROUP block Enter the second-lot powder group 8 GUN NUMBER/CHARGE FIRED block Enter the calibrated charge fired for the howitzer 9 SECOND-LOT CHARGE STANDARD MUZZLE VELOCITY block (Line 6). Enter the second-lot standard muzzle velocity for the calibrated charge. 10 SECOND-LOT CALIBRATED MUZZLE VELOCITY block (Line 7). Enter the second-lot calibrated muzzle velocity from line 7 of the MVS work sheet. 11 SECOND-LOT PIECE MUZZLE VELOCITY Compute the second-lot muzzle velocity variation VARIATION block (Line 8). (line 7 – line 6 = line 8). 12 FIRST-LOT PIECE MUZZLE VELOCITY Enter the first-lot piece muzzle velocity variation from line 5. VARIATION block (Line 9). 13 CHANGE IN MUZZLE VELOCITY VARIATION (Line 10). Determine the change in muzzle velocity variation from the first lot to the second lot (line 8 – line 9 = line 10). 14 SECOND-LOT STANDARD MUZZLE VELOCITY block (Line 11). For all weapons, enter the second-lot standard muzzle velocity from the TFT. 15 CHANGE IN MUZZLE VELOCITY VARIATION block (Line 12). 16 FIRST-LOT MUZZLE VELOCITY VARIATION block (Line 13). Enter the change in muzzle velocity variation from line 10 from the weapon that calibrated the second lot. This value allows us to compensate for propellant efficiency differences between the two lots Enter the first-lot muzzle velocity variation for each weapon from line 5. 17 SECOND-LOT CALIBRATED MUZZLE VELOCITY VARIATION block (Line 14). Record the sums of lines 12 and 13. This gives an inferred muzzle velocity variation to be used for the second lot for each gun (line 12 + line 13 = line 14). 18 CALIBRATED MUZZLE VELOCITY (Line 15). Record the sum of lines 11 and 14. (Apply the inferred MVV plus the standard MV from the TFT to determine an MV.) These are inferred muzzle velocities (line 11 + line 14 = line 15). Legend: DA – Department of the Army MV – muzzle velocity MVS – muzzle velocity system MVV – muzzle velocity variation TFT – tabular firing tables 4-18 TC 3-09.81 13 April 2016 Muzzle Velocity Management Figure 4-10. M90 Velocimeter Work Sheet for Second-Lot Inferred Calibration. 13 April 2016 TC 3-09.81 4-19 Chapter 4 Figure 4-11. Muzzle Velocity Record for Second-Lot Inferred Calibration. 4-20 TC 3-09.81 13 April 2016 Muzzle Velocity Management DETERMINATION OF SHOOTING STRENGTH 4-50. DA Form 2408-4 provides the information to determine the shooting strength of each howitzer. (See table 4-6.) Table 4-6. Determination of Shooting Strength. STEP 1 2 ACTION Determine the pullover gauge reading from DA Form 2408-4 for the specific howitzer if available. See figure 4-6 on page 4-12. DA Form 2408-4 the Pullover gauge reading is 6.147 Determine the equivalent number of EFCs by entering the Approximate Losses in Muzzle Velocity table for the correct weapon in the introduction of the appropriate TFT (figure 4-12). Extract the number of EFCs equivalent to the pullover gauge reading. Interpolate as necessary Note: Ensure that you select the table based on the propellant model you plan on firing. Since the TFT might have multiple tables for Approximate Losses in Muzzle Velocity. Figure 4-12. Approximate Losses in Muzzle Velocity. For the POG (Wear measurement) value of 6.147 the EFC value is 700. Note: If POG is the last entry in DA Form 2408-4, determine shooting strength (SS) by interpolating from the Wear Measurement column to the Muzzle Velocity loss column. 13 April 2016 TC 3-09.81 4-21 Chapter 4 Table 4-6. Determination of Shooting Strength (continued). STEP 3 ACTION Determine the total number of erosion EFCs since the pullover reading. Multiply the number of rounds fire by the erosion factor for the appropriate projectile-propellant charge combination. If unknown, use the pullover gauge reading. Based on Figure 4-6 on page 4-12, DA Form 2408-4 after the last POG the howitzer fired 200 round of charge 4H With this information we refer to Equivalent Service Round Table in the respective TFT and determine the erosion factor (see figure 4-13). Figure 4-13. Equivalent Full Service Rounds Table Notice that for this table the erosion factors are the same for the M232 and M232A1 4H The value of 0.50 is multiplied by the number of rounds fired (200). EFC from rounds fired = EFC Erosion Factor X Number of rounds fired 0.50 X 200=100 EFCs from the rounds fired Note: Raw mathematical values will be determined while solving for the EFC equivalencies only to be expressed to the nearest full EFC when solving for shooting strength in the final solution of the problem. 4 Determine the equivalent cumulative number of EFCs for the specific howitzer by adding the value in step 2 to the value in step 3 For our example, 700 was the EFCs from the POG 6.147 and 100 EFC from the rounds fired 700+100= 800 EFCs 4-22 TC 3-09.81 13 April 2016 Muzzle Velocity Management Table 4-6. Determination of Shooting Strength (continued). STEP 5 ACTION Determine the loss in muzzle velocity by entering the table (figure 4-14 on page 4-23) with the equivalent cumulative number of EFCs; Interpolate as necessary. Figure 4-14. Approximate Losses in Muzzle Velocity The Cumulative EFCs is 800, so we can determine a SS of -6.2 m/s from the Muzzle Velocity Loss column. Note: SS is always negative. 6 The value determined approximates the shooting strength of the howitzer and can be used as the MVV if no propellant efficiencies are available. Repeat step 1-6 for all howitzers and projectile families to be fire. 13 April 2016 TC 3-09.81 4-23 Chapter 4 Table 4-6. Determination of Shooting Strength (continued). STEP 7 ACTION Refer to the MVV Log Book Propellant Efficiency Tab (figure 4-15) and identify the Propellant Model, then the propellant lot and then the appropriated charge and extract the propellant efficiency. Figure 4-15. MACS Propellant Efficiencies (PE) Example Note: DO NOT USE Figure 4-15 to predict MVV’s for firing. Based on our Propellant Model M232A1,and lot IOP09B-031026 firing Charge 4H you would determine a PE of +5.9m/s 8 Determine MVV with Shooting Strength and Propellant Efficiency. MVV is also determine by the algebraic sum of the Shooting Strength and Propellant Efficiency MVV= SS + PE Example SS=-6.2m/s (Step 5) PE= +5.9m/s(Step 7) MVV= -6.2m/s + (+5.9m/s) MVV= -0.3 m/s Legend: DODIC – Department of Defense Identification Code EFC – effective full charge m/s – meters per second MVV – muzzle velocity variation No. – number PE – propellent efficiency POG – pull over gauge rds – rounds SS – shooting strength TFT – tabular firing tables SECTION V: MUZZLE VELOCITY MANAGEMENT 4-51. Muzzle velocity management is the process of tracking the differences in muzzle velocity between the expected muzzle velocity, based on projectile weight, propellant temperature and cannon wear, and the measured muzzle velocity obtained from muzzle velocity system. The goal of muzzle velocity data management is to provide an accurate estimate of the average muzzle velocity for a particular fire mission, based on the weapon, projectile, propellant lot, propelling charge, cannon wear, propellant temperature and projectile weight. 4-52. Three techniques can be used to determine muzzle velocity within the firing unit. The accuracy and complexity of these different techniques varies greatly. Each of the techniques must be understood and applied correctly to the tactical situation. The following is the order of preference and should be used as a guideline. The techniques are listed in order of decreasing preference.  First Lot Calibration (baseline calibration).  Predictive muzzle velocity techniques (when available).  MVV= Shooting Strength (SS) + Propellant Efficiency (PE)  Apply SS  Apply PE  Subsequent lot inferred calibration. 4-24 TC 3-09.81 13 April 2016 Muzzle Velocity Management TRANSFERRING MVVS 4-53. Ideally, every charge should be calibrated. However, this may not always be feasible. Therefore, the calibration of a few charges, one within each charge group that results in an MVV applicable to other charges within a charge group, is imperative. For calibration purposes, there are two categories of charges within a charge group. These are preferred charges and restricted charges. The following guidance is established as an order of preference when selecting a charge to calibrate:  If you know the charge you will be firing calibrate that charge.  If the charge you will be shooting is unknown, calibrate the middle charge of the preferred charge group.  Calibration data determined should only be applied to a subsequent fire mission when the mission meets the following requirement:  It is the same calibrated howitzer  Firing the same calibrated projectile family  Firing the same calibrated propellant lot.  Once calibration data are determined for a particular charge, these data can be transferred to other charges in the same lot. The order of preference for transferring bag charges (i.e. M3A1 and M4A2) is as follows:  Same Charge.  Transfer down 1 charge.  Transfer up 1 charge.  Transfer down 2 charges.  Transfer up 2 charges.  Transfer to any preferred charge.  Transfer from preferred to restrictive charge.  Apply to restricted charge only if calibrated with same restrictive charge.  The rules for transferring MACS vary from those for the bag charges listed above. The restriction of transferring MVVs to another charge within the same lot remains the same. The order of preference for transferring MACS charges is as follows:  All lots of M231 are restricted charges and therefore not preferred to transfer MVVs up or down between 1L and 2L.  All lots of M232 are the charge groups from 3H to 5H, with the preferred charge being 4H for transferring MVVs up or down between 3H and 5H.  All lots of M232A1 are the charge groups from 3H to 5H, with the preffered charge being 4H for transferring MVVs up or down between 3H and 5H. Note: Shooting strength and ammo efficiency make up the achieved MV. With higher charges, there is more erosion but less variance in ammo efficiency. For lower charges, there is less erosion but more variance in ammo efficiency. Therefore, the general overall effect is less variance when transferring down as opposed to up. Note: MVVs should not be transferred from a restricted charge to any other charge on the basis of the nature (large round-to-round variances) of restricted charges. UPDATING PROPELLANT EFFICIENCIES DATA 4-54. Once determined, the calibration data represent the best indicator of the expected MVV. But the MVV is not valid forever since the howitzer shooting strength changes as more rounds are fired. Calibration data can be made indefinitely valid if the shooting strength of the howitzer is determined at the time of calibration. The shooting strength is subtracted from the MVV and this will provide an accurate PE that can be use later. This is done by modifying the formula MVV= SS+ PE. It is important to isolate the propellant efficiencies (MVV – Shooting Strength = Propellant Efficiency) after an MVV has been 13 April 2016 TC 3-09.81 4-25 Chapter 4 captured for a specific howitzer. This math procedure may be performed in the bottom “Remarks” field of the DA Form 4982. If logged correctly, isolating propellant efficiencies may provide the battery or battalion a more accurate MVV when only predictive MVV’s are possible (see table 4-7). An accurate propellant efficiency may provide a more accurate MVV than just calculating shooting strength. Table 4-7. Determining Unit PE After a Calibration. STEP ACTION 1 Record First Lot calibration (figure 4-16) as described in Table 4-4 on page 4-17. Figure 4-16. Muzzle Velocity Record for a First Lot Calibration, Line 5. 2 In the lower computational space record formula: PE = MVV – SS (See below Figure 417). 3 Determine an accurate SS for each weapon. As discussed in Table 4-6 on page 4-21. 4 Determine PE for each gun and battery average PE (figure 4-17). Figure 4-17. Muzzle Velocity Record Remarks Block. Note: Disregard a PE outside (±) 3 m/s from battery average. is disregarded and re-average battery without the disregarded PE 5 Determine The average PE for this example is -1.3 m/s Legend: m/s – meters per second MVV – muzzle velocity variation PE – propellent efficiency SS – shooting strength Note: Propellant efficiency values are transferable since they are independent of a shooting strength, variable and may provide more accurate data to enable massing of fires when conducting battalion level missions MVV LOGBOOK 4-55. Once MV data have been determined, these data are used for numerous techniques. MV data must be recorded on DA Form 4982 which is then filed in an MV logbook. The MV logbook allows for quick referencing of howitzer performance when firing a particular projectile family-propellant lot-charge combination. Historical MV’s from the MVV logbook can be applied to missions if they match the projectile-family-propellant lot-charge combination. If not a match, they may be transferred according to the order of preference found later in this chapter. Using historical MV’s may be more accurate than predictive MVV techniques. The major sections in the MV logbook are for the projectile families. Each one of the sections should be tabbed for each authorized propellant type-charge group for the projectile family. See figures 4-18 and 4-19 (page 4-27) below for an example of FDC Record keeping:  Organizing the logbook. The FDO separates the major portions of his logbook by projectile families. 4-26 TC 3-09.81 13 April 2016 Muzzle Velocity Management Figure 4-18. Muzzle Velocity Variation (MVV) Logbook Major Tabs.  Tabbing the logbook. Each section (Projectile Family) of the MVV logbook is tabbed with all possible powder models. Figure 4-19. Muzzle Velocity Variation (MVV) Logbook Tabs. FREQUENCY OF CALIBRATION 4-56. Ideally, calibration occurs continuously. If that is impractical or impossible, the following methods identify when to consider calibrating. 4-57. Initial Receipt or Retubing. All new howitzers of a given caliber and model will not necessarily develop the same muzzle velocity because of the tolerances that are allowed in the size of the powder chamber and in the dimensions of the bore. Therefore, howitzers should be calibrated as soon as possible after receipt or when retubed. Muzzle velocities should be recorded on DA Form 4982 and DA Form 49821 with accurate bumper number and weapon tube numbers for proper logging. 4-58. Change in Propellant Lot. Calibration should be conducted as soon as possible after an uncalibrated propellant lot is received. 4-59. New Projectile Family. Calibration should be conducted if a new projectile; for example, M825A1 smoke (projectile family M795), is received for which there are no previous MV records for that projectile family. 4-60. Annually. Any piece in service should be recalibrated at least annually. The primary factor contributing to the loss in muzzle velocity for a piece is the number of rounds that have been fired through the tube and the charges used in firing them. Higher charges increase tube wear, which, in turn, tends to decrease muzzle velocity. Guns, because of their higher velocities, tend to display tube wear more quickly than howitzers. If a great deal of firing takes place, recalibration will be needed more often than annually. Methods of determining when recalibration may be needed are outlined below. The following situations assume that firing takes place with a previously calibrated projectile family-propellant lot. 4-61. Changes in velocity error (VE). If an accurate record of the changes in velocity error (VE) determined from concurrent met solutions is maintained, it may be used as a guide for determining the need for recalibration. When the velocity loss since the last calibration is equivalent to 2 range probable errors, the need for recalibration is indicated. (An indicator of this is a loss of +/-1.5 m/s, which generally approximates 2 probable errors in range.) 4-62. Tube Wear. The extent of tube wear near the beginning of the rifling of the bore indicates the loss in muzzle velocity and the remaining tube life. Precise measurement of the distance between the lands in the 13 April 2016 TC 3-09.81 4-27 Chapter 4 bore near the start of the rifling can be made with a pullover gauge. Field maintenance has this gauge and makes the measurement. The wear measurement, when compared with the data in the “wear” table (Approximate Losses in Muzzle Velocity table) in the introduction of each firing table, can be used in estimating the loss in muzzle velocity. 4-63. EFCs. A change in the number of erosion EFC service rounds as depicted in the weapon record book may also indicate a need for recalibration. (Refer to paragraph 4-3 for more information about EFCs.) The change in erosion EFC rounds compared with data in the Approximate Losses in Muzzle Velocity table (in the introduction of each TFT) that corresponds to a loss of 1.5 m/s in muzzle velocity may indicate a need for recalibration. A loss of 1.5 m/s in MV generally equates to the effects of 2 probable errors in range (2 PER) 4-28 TC 3-09.81 13 April 2016