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 450 of 775
TM 9--2350--311--10
3--50
Change 6
3--6
ARMAMENT AND CAB MAINTENANCE — CONTINUED
3--6.5
Estimating Remaining Round Life of Cannon Tubes
Cannon tubes must be inspected and borescoped within 180 days prior to initial firing and within each 180 day interval
when utilized for continuous or recurring firing. Notify unit maintenance for borescoping (TM 9--1000--202--14).
WARNING
Do not fire beyond cannon tube life.
NOTE
•
Condemnation of the cannon tube is based on fatigue life in Equivalent Full Charge (EFC)
rounds or wear life (pullover gauge measurement), whichever occurs first.
•
Breech assemblies which have been modified from the M185 cannon assembly to the
M284 cannon assembly may have EFC condemnation criteria stamped on the breech
assembly and DA Form 2408--4.
The method for determining remaining life for cannon tubes is to convert rounds fired to Equivalent Full Charge (EFC)
rounds. Convert to EFC rounds and enter in Weapon Record Data DA Form 2408--4 in accordance with
DA Pam 750--8. Since the condemnation criteria as listed in the table below is based on EFC rounds fired, the zone for
each round fired must be entered on DA Form 2408--4, and the total roundsfired byzone mustbe carriedforward tothe
new data card upon closeout in accordance with DA Pam 750--8.
Condemnation Criteria for Cannon Tube and Breech Assembly
Model
No.
EFC Life of
Cannon Tube
EFC Factor
Breech Assembly Life
M185
6375 rds
Zone 1--6
=
0.25
Zone 7
=
0.75
Zone 8
=
1.00
Original and two retubings
M284
2650 rds
Zone 1
(M231)
=
0.05
Original with one retubing
Zone 2
(M231)
=
0.15
Zone 3
(M232/M232A1) =
0.10
Zone 4
(M232/M232A1) =
0.25
Zone 5
(M232/M232A1) =
1.00
Zone 3G--5G
(3A1)
=
0.05
Zone 3W--6W
(M4A2)
=
0.05
Zone 7W
(M4A2)
=
0.15
Zone 8/7R
(M119A1/A2)
=
0.25
Zone 8R/8S
(M203/A1)
=
1.00
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