TM-9-2350-311-20-2

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

TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS

DECEMBER 1993

TM-9-2350-311-20-2 - Page 691 of 828

TM 9–2350–311–20–2

Change 2

18–21

c.

Checking Synchronization of the M145/M145A1 Telescope Mount

1

Elevate cannon tube to 400 mils using M1A1 gunner’s quadrant (1) (end-for-end correction applied) (breech

ring correction applied) placed on breech ring quadrant seats (3).

NOTE

With M1A1 gunner’s quadrant on M145/M145A1 telescope mount quadrant seats, the bubble in the

M1A1 gunner’s quadrant can be read more accurately by observing M1A1 gunner’s quadrant

bubble with inspection mirror.

2

Place M1A1 gunner’s quadrant (1) with reading of 400 mils (end-for-end correction applied) (breech ring

correction removed) on M145/M145A1 telescope mount (5) quadrant seats (6).

3

Center bubble in M145/M145A1 telescope mount (5) cross-level vial (7).

4

Bubble (4) on M1A1 gunner’s quadrant (1) should also be centered. If bubble on M1A1 gunner’s quadrant is

not centered, turn micrometer knob (12) until bubble on M1A1 gunner’s quadrant is centered.

5

Record reading of M1A1 gunner’s quadrant (1).

6

Repeat steps 1 through 5 for elevations at 800 and 1200 mils.

7

Compare elevation readings taken at 400 mils, 800 mils, and 1200 mils.

(a)

If the error at each of the three elevations does not exceed

±

0.5 mils, no adjustment is necessary.

(b)

If the error at any elevation exceeds

±

0.5 mils adjustment is necessary. Adjust the M145/M145A1 tele-

scope mount (5) (para 18–4d.).

3

1

5

12

1

4

7

6