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 464 of 775

TM 9-2350-311-10

3-6 ARMAMENT AND CAB MAINTENANCE — CONTINUED

3-6.8

Breech Mechanism — Continued

a. Disassembly — Continued

5

6

7

• Never attempt to disassemble the breech mechanism with breech partially or fully closed.

• Since all spring tension has been released, be extra careful when opening breechblock. Use

operating handle and support breechblock as it is being opened. Otherwise, breechblock

will slam open and carrier assembly may be damaged.

With one individual supporting breechblock (9) and another individual slowly using operating handle (10),

open breechblock until rollers (11) are eased into operating cam (12) path. Return operating handle to

stowed position.

While supporting breechblock (9), raise operating cam (12) slightly until rollers (11) have cleared

operating cam path. Rotate breechblock to UNLOCKED position.

While holding operating cam (12) slightly upward, depress detent (13) using punch and rotate

breechblock (9) to LOCKED position.

NOTE

• It is not necessary to remove the plunger assembly from the cannon assembly if only the

spindle assembly has to be removed for inspection or replacement.

• Perform step 8 for the M109A2/M109A3/M109A4 M185 cannon assembly if only the nut and

spindle assembly are to be removed. If housing and firing group block are to be removed, go

to step 11.

3-6 0