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 288 of 775

TM 9-2350-311-10

2-12 PREPARATION FOR FIRING — CONTINUED

2-12.2 Boresighting — Continued

g. Boresighting — Distant Aiming Point Method — Continued

NOTE

Either the breech bore sight or the firing pin hole may be used as a rear sighting guide during

boresighting.

3

Look through the center hole of the breech bore sight (2) or through firing pin hole as applicable, and

elevate and traverse the cannon tube until the muzzle brake (4) boresight crosshairs (3) are on the

upper left-hand corner of the distant aiming point (38).

4

Center bubbles of cross-level (11) and pitch level (12) by turning cross-level mechanism knob (34) and

pitch level knob (35).

5

Rotate azimuth knob (16) and elevation knob (17) on M117/M117A2 panoramic telescope (18) to lay

reticle on left edge of distant aiming point (38).

6

Check that muzzle brake (4) crosshairs (3) are still on the upper left-hand corner of distant aiming point

(38).

7

Azimuth counter (19) should read 3200 mils. If it doesn’t, remove cover (20) from boresight detent shaft

(21) insert small screwdriver and depress boresight detent shaft. Turn until 3200 mils appears in

azimuth counter. Recheck sight picture to be sure M117/M117A2 panoramic telescope (18) is still

boresight.

in

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