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 294 of 775

TM 9-2350-311-10

2-12 PREPARATION FOR FIRING — CONTINUED

2-12.3

Standard Angie Method — Continued

b.

Boresighting Using the Standard Angle Method (Field Situation)

NOTE

Although boresighting using the standard angle method is acceptable, boresighting using the

distant aiming point method or test target method (para 2-12.2) should be accomplished as

soon as is feasible.

1

Ensure gun trunnions have 90 mils cant or less.

NOTE

The standard angle method of boresighting is accurate only to the extent that the relationship

between recoiling and non-recoiling parts remains constant. The distance from the

M117/M117A2 panoramic telescope to the muzzle brake remains the same, so the angle from

the M117/M117A2 panoramic telescope to the muzzle brake should not change.

2

Ensure scribe lines on variable recoil cylinder (2) and machine bushing (3) aline.

3

Ensure scribe lines on muzzle brake (4) and cannon tube (5) aline.

4

Place the cannon tube (5) at 0 mils using the M1A1 gunner’s quadrant.

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