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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--170 Change 2 2--12 PREPARATION FOR FIRING — CONTINUED 2--12.2 Boresighting a. Preliminary Procedure 1 Make sure howitzer cant is no more than 90 mils. (o) Observe howitzer and determine which side is higher. (p) Place M1A1 gunner’s quadrant on breech ring cross-level seats with the direction of fire indicator pointing toward high side of howitzer. (q) Place cross-level arm on zero and ensure micrometer knob indicates zero. Move cross-level arm in increments of 10 mils until bubble moves to the opposite end of vial. (r) Move cross-level arm back down one 10 mil increment, and use the micrometer knob to level bubble. (s) Observe reading on M1A1 gunner’s quadrant. (t) If cant is greater than 90 mils, howitzer must be moved to more level ground. 2 Open breechblock (1) and install breech bore sight (2). 3 Fasten crosshairs (3) to muzzle brake (4) at witness marks. 4 Ensure M117/M117A2 panoramic telescope and M118A2/M118A3 elbow telescope are installed (para 2--11.1 and 2--11.2). 3 2 4 1