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--180 Change 6 2--12 PREPARATION FOR FIRING — CONTINUED 2--12.2 Boresighting — Continued d. Checking Boresight of M117/M117A2 Panoramic Telescope Using the M140/M140A1 Alinement Device WARNING The M140 alinement device is radioactively illuminated. Check for loss of luminescence, breakage, damage, or defects. If present, follow the procedures on pages b and c. 1 Inspect mating surfaces of M140/M140A1 alinement device (27) and dovetail door wedge (28) for burrs. Wipe mating surfaces clean. If dovetail door wedge has burrs, notify unit maintenance. 2 Install M140/M140A1 alinement device (27) on dovetail door wedge (28). 2.1 If using ERLS version, depress button (32.1) to activate. NOTE M117/M117A2 panoramic telescope parallax may occur between M117/M117A2 panoramic telescope and M140/M140A1 alinement device. This may happen as panoramic telescope ballistic cover is rotated away from perpendicular to line of sight of M117/M117A2 panoramic telescope. Panoramic telescope ballistic cover should be kept perpendicular to M140/M140A1 alinement device during boresighting to minimize this problem. Tolerance is ± 0.5 mil. 3 Position panoramic telescope ballistic cover (29) perpendicular to M140/M140A1 alinement device (27) to eliminate error that may be induced by light refraction through glass.