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 502 of 775

TM 9–2350–311–10

3–98

Change 3

3–7

FIRE CONTROL ALINEMENT TESTS AND MEASUREMENTS — CONTINUED

3–7.5

Leveling the Cannon Tube — Continued

b.

Leveling the Cannon Tube Using the M1A1 Gunner’s Quadrant — Continued

WARNING

The breechblock must be open and the operating handle left unlocked. To prevent injury to

personnel, be careful not to lift up on operating cam before securing operating handle after

leveling cannon tube.

2

Unlatch operating handle (18) enough to place M1A1 gunner’s quadrant (13).

3

Move M1A1 gunner’s quadrant (13) to elevation seats (19) on breech ring and center the elevation

bubble (3) by moving micrometer knob (20). The difference between 0 mils at muzzle brake end and the

reading taken at breech ring is the measured correction.

4

Add M1A1 gunner’s quadrant (13) correction and measured corrections. For example:

M1A1 gunner’s quadrant correction

– 0.4

Measured correction

+ 1.9

Place on M1A1 gunner’s quadrant

+ 1.5

NOTE

•

Failure to compensate for measure correction will result in misalinement on weapon being

checked.

•

The measured correction shall be determined again when a breech is retubed.

5

Record the measured correction in the remarks column on DA Form 2408–4. Refer to the measured

correction when making elevation settings with the M1A1 gunner’s quadrant (13).

NOTE

Breech is completely closed when witness marks on breech ring and breechblock aline.

6

If necessary, open breech and close completely.

19

13

3

18

WITNESS

MARKS

20