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 296 of 775

TM 9-2350-311-10

2-12 PREPARATION FOR FIRING — CONTINUED

2-12.3

Standard Angle Method — Continued

b.

Boresighting Using the Standard Angle Method (Field Situation) — Continued

NOTE

A parallax shield can be made to prevent eye movement in two ways. One is to use a dust cap

with a hole in the center. The second is to use a small opening marked off with strips of tape.

8

Using a parallax shield, turn the M117/M117A2 panoramic telescope (11) azimuth knob (12) to aline the

vertical hairline (13) of the M117/M117A2 panoramic telescope on the farthest left edge of the muzzle

brake (4). Aline horizontal hairline (14) of the M117/M117A2 panoramic telescope on the top edge of the

muzzle brake by turning the M117/M117A2 panoramic telescope elevation knob (15).

9

Note the reading on the M117/M117A2 panoramic telescope (11) azimuth counter (16). If the reading

equals the standard angle of deflection, the howitzer is boresighted. If the reading does not equal the

standard angle of deflection, go to step 10.

10

Using a screwdriver, depress the boresight detent shaft (17) and adjust the azimuth counter (16) until it

displays the standard angle of deflection. Repeat step 8. The weapon is now boresighted.

2-198

Change 2