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*FM 23-90/TO 11W2-5-13-21

FIELD MANUAL
NO. 23-90
TECHNICAL ORDER
NO. 11W2-5-13-21
HEADQUARTERS
DEPARTMENT OF THE ARMY
AND THE AIR FORCE
WASHINGTON, DC, 1 March 2000

FM 23-90

MORTARS

Table of Contents


PREFACE

 

CHAPTER 1

INTRODUCTION

Section I General Doctrine
  1-1. Effective Mortar Fire
  1-2. Mortar Positions
Section II Indirect Fire Team
  1-3. Applications
  1-4. Team Mission
Section III Safety Procedures
  1-5. Duties of the Safety Officer and Supervisory Personnel
  1-6. Ammunition Care and Handling
  1-7. Field Storage of Ammunition

CHAPTER 2

SIGHTING AND FIRE CONTROL EQUIPMENT

Section I Compass, M2
  2-1. Characteristics
  2-2. Description
  2-3. Use
Section II Aiming Circles, M2 and M2A2
  2-4. Characteristics
  2-5. Description
  2-6. Use
  2-7. Accessory Equipment
  2-8. Setup and Leveling of Aiming Circle
  2-9. Declination Constant
  2-10. Orienting of the Instrument on Grid North to Measure Grid Azimuth to Objects
  2-11. Measurement of Horizontal Angle Between Two Points
  2-12. Orienting of the 0-3200 Line on a Given Grid Azimuth
  2-13. Orienting of the 0-3200 Line on a Given Magnetic Azimuth
  2-14. Verifying the Lay of the Platoon
  2-15. Orienting by Orienting Angle
  2-16. Disassembly of Aiming Circle
  2-17. Care and Maintenance
Section III Sightunits
  2-18. Sightunit, M53-Series
  2-19. Operation of M53 Sightunit
  2-20. Care and Maintenance of M53 Sightunit
  2-21. Sightunit, M64-Series
  2-22. Sightunit, M67
Section IV Boresights
  2-23. Boresight, M45-Series
  2-24. Boresight, M115
  2-25. Principles of Operation
  2-26. Installation
  2-27. Sight Calibration
  2-28. Boresight Method of Calibration
  2-29. Calibration for Deflection Using the M2 Aiming Circle
Section V Other Equipment
  2-30. Instrument Light, M53E1
  2-31. Aiming Posts, M14 and M1A2
  2-32. Aiming Post Lights, M58 and M59
Section VI Laying the Section
  2-33. Reciprocal Laying
  2-34. Reciprocal Laying on a Grid Azimuth
  2-35. Reciprocal Laying on a Magnetic Azimuth
  2-36. Reciprocal Laying Using the Orienting Angle
  2-37. Reciprocal Laying Using the Mortar Sights
  2-38. Reciprocal Laying Using the M2 Compass
  2-39. Placing Out Aiming Posts
  2-40. Alternate Method of Placing Out Aiming Posts
  2-41. Correction for Displacement of Sight
Section VII Loading and Firing
  2-42. Firing the Mortar
  2-43. Target Engagement
  2-44. Execution of Fire Commands
  2-45. Arm-and-Hand Signals
  2-46. Subsequent Fire Commands
  2-47. Repeating and Correcting of Fire Commands
  2-48. Reporting of Errors in Firing
  2-49. Night Firing

CHAPTER 3

60-mm MORTAR, M224

Section I Squad and Section Organization and Duties
  3-1. Organization
  3-2. Duties
Section II Components
  3-3. Tabulated Data
  3-4. Cannon Assembly, M225
  3-5. Baseplate, M7
  3-6. Baseplate, M8
  3-7. Bipod Assembly, M170
Section III Operation
  3-8. Premount Checks
  3-9. Mounting of the Mortar
  3-10. Safety Checks Before Firing
  3-11. Small Deflection and Elevation Changes
  3-12. Large Deflection and Elevation Changes
  3-13. Referring of the Sight and Realignment of Aiming Posts
  3-14. Malfunctions
  3-15. Removal of a Misfire
  3-16. Dismounting and Carrying of the Mortar
Section IV Ammunition
  3-17. Classification
  3-18. Color Codes
  3-19. Preparation of Ammunition
  3-20. Types of Fuzes
  3-21. Standard B Ammunition
  3-22. Care and Handling

CHAPTER 4

81-mm MORTAR, M252

Section I Squad and Section Organization and Duties
  4-1. Organization
  4-2. Duties
Section II Components
  4-3. Tabulated Data
  4-4. Cannon Assembly, M253
  4-5. Mount, M177
  4-6. Baseplate, M3A1
Section III Operation
  4-7. Premount Checks
  4-8. Mounting of the Mortar
  4-9. Safety Checks Before Firing
  4-10. Small Deflection and Elevation Changes
  4-11. Large Deflection and Elevation Changes
  4-12. Referring of the Sight and Realignment of Aiming Posts Using M64 Sight
  4-13. Malfunctions
  4-14. Removal of a Misfire
  4-15. Dismounting of the Mortar
Section IV Ammunition
  4-16. Classification
  4-17. Function
  4-18. High-Explosive Ammunition
  4-19. Red/White Phosphorus Ammunition
  4-20. Illuminating Ammunition
  4-21. Types of Fuzes
  4-22. Characteristics of Proximity Fuzes
  4-23. Fuze Wrench and Fuze Setter
  4-24. Preparation of Ammunition
  4-25. Care and Handling

CHAPTER 5

81-mm MORTAR, M29A1

Section I Squad and Section Organization and Duties
  5-1. Organization
  5-2. Duties
Section II Components
  5-3. Tabulated Data
  5-4. Cannon Assembly, M29A1
  5-5. Bipod Assembly, M23A1
  5-6. Baseplate, M3
Section III Operation
  5-7. Premount Checks
  5-8. Mounting of the Mortar
  5-9. Safety Checks Before Firing
  5-10. Small Deflection and Elevation Changes
  5-11. Large Deflection and Elevation Changes
  5-12. Referring of the Sight and Realignment of Aiming Posts Using M53 Sight
  5-13. Malfunctions
  5-14. Removal of a Misfire
  5-15. Dismounting of the Mortar
Section IV Ammunition
  5-16. Function
  5-17. High-Explosive Ammunition
  5-18. White Phosphorus Ammunition
  5-19. White Phosphorus Ammunition
  5-20. Types of Fuzes
  5-21. Characteristics of Proximity Fuzes
  5-22. Fuze Wrench and Fuze Setter
  5-23. Preparation of Ammunition
  5-24. Care and Handling

CHAPTER 6

4.2-INCH MORTAR, M30

Section I Squad and Section Organization and Duties
  6-1. Organization
  6-2. Duties
  6-3. Section Drill and Section Leader Duties
Section II Components
  6-4. Tabulated Data
  6-5. Mortar Cannon, M30
  6-6. Mortar Mount, M24A1
Section III Operation of Ground-Mounted Mortar
  6-7. Mounting of the Mortar
  6-8. Safety Checks Before Firing
  6-9. Small Deflection Change
  6-10. Large Deflection and Elevation Changes
  6-11. Loading and Firing of M329A2 Round
  6-12. Malfunctions
  6-13. Removal of a Misfire
  6-14. Dismounting of the Mortar
Section IV Mortar Carriers, M106, M106A1, and M106A2
  6-15. Description
  6-16. Tabulated Data
Section V Operation of Carrier-Mounted Mortar
  6-17. Mortar and Vehicular Mount
  6-18. Maintenance
  6-19. Placement of Mortar Into Firing Position on Carrier
  6-20. Laying for Deflection and Elevation
  6-21. Removal of a Misfire (Carrier-Mounted)
  6-22. Mounting of Mortar on Carrier From Ground-Mounted Position
  6-23. Dismounting of Mortar From Carrier
  6-24. Preparation for a March Order From Ground-Mounted Position
  6-25. Safety Checks
  6-26. Measurement of Minimum and Maximum Elevations
  6-27. Squad Formations
  6-28. Dismounted Mortar Squad
  6-29. Reciprocally Laying the Mortar Carrier Section
Section VI Ammunition
  6-30. Classification
  6-31. Types of Fuzes
  6-32. Preparation of Ammunition
  6-33. Care and Handling

CHAPTER 7

120-mm MORTAR, M120

Section I Squad and Section Organization and Duties
  7-1. Organization
  7-2. Duties
Section II Components
  7-3. Tabulated Data for the 120-mm Mortar, M120
  7-4. Barrel Assembly, M298
  7-5. Bipod Assembly, M191 (Carrier-/Ground-Mounted)
  7-6. Bipod Assembly, M190 (Ground-Mounted)
  7-7. Baseplate, M9
Section III Operations
  7-8. Placing a Ground-Mounted 120-mm Mortar Into Action
  7-9. Performing Safety Checks on a Ground-Mounted 120-mm Mortar
  7-10. Performing Small Deflection and Elevation Changes on a Ground-Mounted 120-mm Mortar
  7-11. Performing Large Deflection and Elevation Changes on a Ground-Mounted 120-mm Mortar
  7-12. Malfunctions on a Ground-Mounted 120-mm Mortar
  7-13. Performing Misfire Procedures on a Ground-Mounted 120-mm Mortar During Combat
  7-14. Loading and Firing the Ground-Mounted 120-mm Mortar
  7-15. Taking the 120-mm Mortar Out of Action
Section IV Mortar Carrier, M1064A3
  7-16. Description
  7-17. Tabulated Data for the M1064A3 Carrier
Section V Operation of a Carrier-Mounted 120-mm Mortar
  7-18. Mortar and Vehicular Mount
  7-19. Maintenance
  7-20. Placing Carrier-Mounted 120-mm Mortar Into Action
  7-21. Lay for Deflection and Elevation on a Carrier-Mounted 120-mm Mortar
  7-22. Performing Misfire Procedures on a Carrier-Mounted 120-mm Mortar During Combat
  7-23. Mounting of the Mortar From a Carrier to a Ground-Mounted Position
  7-24. Taking the Mortar Out of Action (Ground-Mounted to M1064A3 Carrier-Mounted)
  7-25. Performing Safety Checks on a Carrier-Mounted 120-mm Mortar
  7-26. Reciprocally Laying the Mortar Carrier Section
Section VI Ammunition
  7-27. Classification
  7-28. Authorized Cartridges
  7-29. Preparation for Firing
  7-30. Loading and Firing
  7-31. Unfired Cartridges
  7-32. Care and Handling of Cartridges
  7-33. Fuzes
  7-34. Setting Fuzes
  7-35. Resetting Fuzes

CHAPTER 8

FIRE WITHOUT A FIRE DIRECTION CENTER

Section I Fire Procedures
  8-1. Advantages and Disadvantages
  8-2. Firing Data
  8-3. Observer Corrections
  8-4. Initial Fire Commands
  8-5. Fire Commands
  8-6. Fire Control
  8-7. Movement to Alternate and Supplementary Positions
  8-8. Squad Conduct of Fire
  8-9. Reference Line
  8-10. Fire Adjustment
  8-11. Squad Use of Illumination and Smoke
  8-12. Attack of Wide Targets
  8-13. Attack of Deep Targets
Section II Direct-Lay Method
  8-14. Step 1: Initial Firing Data
  8-15. Step 2: Referring the Sight
  8-16. Step 3: Bracketing the Target
  8-17. Step 4: Fire for Effect
Section III Direct-Alignment Method
  8-18. Mortar Dismounted
  8-19. Mortar Mounted
  8-20. Natural Object Method
Section IV Adjustment of Range
  8-21. Range Spottings
  8-22. Miscellaneous Spottings
  8-23. Bracketing Method
  8-24. Creeping Method of Adjustment
  8-25. Normal Fire Commands
  8-26. Modified Fire Commands
  8-27. Fire Control
  8-28. Establishment of a Reference Line and Shifting From That Line
  8-29. Ladder Method of Adjustment

CHAPTER 9

GUNNER'S EXAMINATION

Section I Preparatory Instruction
  9-1. Methods of Instruction
  9-2. Prior Training
  9-3. Preparatory Exercises
  9-4. Examining Board
  9-5. Location and Date
  9-6. Eligible Personnel
  9-7. Qualification Scores
  9-8. General Rules
Section II Gunner's Examination With Ground-Mounted Mortar
  9-9. Subjects and Credits
  9-10. Equipment
  9-11. Organization
  9-12. Procedure
  9-13. Mounting of the Mortar
  9-14. Small Deflection Change
  9-15. Referring of the Sight and Realignment of Aiming Posts
  9-16. Large Deflection and Elevation Changes
  9-17. Reciprocal Laying
Section III Gunner's Examination With the Track-Mounted Mortar
  9-18. Subjects and Credits
  9-19. Equipment
  9-20. Organization
  9-21. Procedure
  9-22. Placement of Mortar Into a Firing Position From Traveling Position
  9-23. Small Deflection Change
  9-24. Referring of the Sight and Realignment of Aiming Posts
  9-25. Large Deflection and Elevation Changes
  9-26. Reciprocal Laying
  9-27. Support Squad

APPENDIX A

TRAINING DEVICES

APPENDIX B

MORTAR TRAINING STRATEGY

GLOSSARY

REFERENCES

AUTHENTICATION

DISTRIBUTION RESTRICTION: Approved for public release, distribution is unlimited.


*This publication supersedes FM 23-90/TO 11W2-5-13-21, 19 September 1990; and TC23-18, 24 August 1967.



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