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 3-7 FIRE CONTROL ALINEMENT TESTS AND MEASUREMENTS — CONTINUED 3-7.3 Leveling Gun Trunnions — Continued a. Plumbline Method-Continued 15 Look through the breech bore sight (3) and check for proper alinement like B. Correct as required (steps 12 or 13). 16 Continue to elevate cannon tube (6) manually in 100 mil increments up to 600 mils, while observing plumbline (4). Jack the weapon as required to keep vertical crosshair (14) parallel to plumbline. 17 Slowly depress cannon tube (6) to zero mils while observing plumbline (4). The crosshair should track the plumbline. If it does, the gun trunnions are level. If it does not track, repeat steps 14 through 17 until the proper alinement like B is obtained without moving the jacks (7). If plumbline cannot be tracked, notify unit maintenance. 3-91