TM-9-2350-311-10

HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5

TECHNICAL MANUAL; OPERATOR’S MANUAL

NOVEMBER 1994

TM-9-2350-311-10 - Page 278 of 775

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.