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--178 Change 6 2--12 PREPARATION FOR FIRING — CONTINUED 2--12.2 Boresighting — Continued c. Checking M140/M140A1 Alinement Device While Boresighting on Test Target — Continued 4 Check alinement of M140/M140A1 alinement device (27) reticle against reticle of M117/M117A2 panoramic telescope (18) laid on left hand butterfly aiming diagram (15) of test target. Reticles should aline within 0.5 mil. 5 Remove M140/M140A1 alinement device (27) from in front of panoramic telescope ballistic cover (29) and install on dovetail door wedge (28) in front of M42 tank periscope (30) cover door (31).