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 392 of 775
TM 9-2350-311-10
2-20 OPERATION IN UNUSUAL ENVIRONMENT/WEATHER — CONTINUED
2-20.4 Operation in Extreme Cold — Continued
f. Howitzer Cannon in Extreme Cold Weather
1
2
3
4
5
6
7
NOTE
Extreme cold weather temperatures between –20 to -65° F (–29 to -54° C) slows down
extension of counter recoil to its maximum length for proper buffering action. Operate breech
mechanism manually, observing the following instructions when firing first several rounds to
warm buffer fluid to operating temperature.
Prepare weapon for firing before opening breech, loosen self-locking nut (21) on cam tension adjuster
screw.
Manually open breech, load projectile and charge; close breech.
Use Zone 5 or below in cold weather to prevent malfunctions.
Before inserting primer, raise operating cam (22) until it clears roller (23) by 1/16 to 1/8 inch (1.59 to 3.18
mm) above rollers. Turn cradle cam stop (24) clockwise until clearance of 1/16 to 1/8 inch (1.59 to 3.18
mm) is maintained between operating cam and roller. Tighten self-locking nut (21).
Insert primer and continue standard firing procedures.
After weapon returns to battery, lift operating cam (22) and loosen self-locking nut (21). Turn cradle cam
stop (24) counterclockwise until roller (23) engages in operating cam approximately 3/16 inch (4.8 mm),
to permit operating cam and roller to hold breech open to reload weapon. Tighten self-locking nut.
Repeat steps 2 through 5 for each round fired, until buffer fluid is warmed to operating temperature.
Buffer fluid can be warmed to operating temperature as follows:
Temperature
No. of Rounds
Total Elapsed Time
–20° F (–29° C)
4
9 minutes
-30° F (-34° C)
5
12 minutes
-40° F (-40° C)
6
15 minutes
-50° F (-46° C)
7
21 minutes
-60° F (-51° C)
8
24 minutes
After final “warm-up” round is fired, repeat step 5 to ensure proper clearance of at least 3/16 inch (4.8
mm) but not more than 1/4 inch (6.35 mm) between top of roller (23) at top of operating cam (22) path is
2-286
maintained.
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