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 125 of 775

TM 9-2350-311-10

Item

No.

23

Interval

Before

Table 2-1. PREVENTIVE MAINTENANCE CHECKS AND SERVICES

FOR M109 SELF-PROPELLED HOWITZER - CONTINUED

Location

Item to Check/

Service

Firing

Mechanism,

Firing Block

Assembly, And

Primer Chamber

Crewmember

Procedure

CANNONEER NO. 1

a. With firing block assembly (1) in center position,

push firing mechanism (2) into firing block as-

sembly and rotate clockwise to remove.

Remove lock pin and firing pin (3) and check to

see if firing pin is damaged or broken.

NOTE

The M35 firing mechanism is used with the

M109A2/M109A3/M109A4 M178 mount/M185

cannon assembly. The M49 firing mechanism

is used with the M109A5 M182 mount/M284

cannon assembly.

b. Replace firing pin (3) and firing mechanism (2).

Place firing mechanism in firing position.

c. Attach lanyard and check operation of firing

mechanism with a steady pull on the lanyard. A

click will be heard and firing mechanism (2)

should recock.

d. Check follower assembly (4) operation.

e. Check primer chamber (5) for rust and powder

fouling.

f.

Clean primer chamber (5) by inserting reamer

assembly into primer chamber as far as it will

go. Rotate briskly.

g. Slide firing block assembly (1) back and forth to

check for smooth movement. If firing block as-

sembly binds, notify unit maintenance.

Not Fully Mission

Capable If:

Firing mecha-

nism (2) or fol-

ower assembly

4) is unservice-

able or missing.

Firing pin (3) is

damaged or bro-

ken.

Change 2 2-39