TM-9-2350-311-10 M109 Operator's Manual for M109A2, M109A3, M109A4 and M109A5 Download
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TM 9-2350-311-10 2-12 PREPARATION FOR FIRING — CONTINUED 2-12.3 Standard Angie Method — Continued b. Boresighting Using the Standard Angle Method (Field Situation) NOTE Although boresighting using the standard angle method is acceptable, boresighting using the distant aiming point method or test target method (para 2-12.2) should be accomplished as soon as is feasible. 1 Ensure gun trunnions have 90 mils cant or less. NOTE The standard angle method of boresighting is accurate only to the extent that the relationship between recoiling and non-recoiling parts remains constant. The distance from the M117/M117A2 panoramic telescope to the muzzle brake remains the same, so the angle from the M117/M117A2 panoramic telescope to the muzzle brake should not change. 2 Ensure scribe lines on variable recoil cylinder (2) and machine bushing (3) aline. 3 Ensure scribe lines on muzzle brake (4) and cannon tube (5) aline. 4 Place the cannon tube (5) at 0 mils using the M1A1 gunner’s quadrant. 2-196