PS Magazine - TB 43-PS-682

PS, The Preventative Maintenance Monthly

ISSUE 682

SEPTEMBER 2009
PS Magazine - TB 43-PS-682 - Page 4 of 33
4
PS 682
SEP 09
You need an open breech to allow fresh air to be drawn into the gun tube. So if the
stub base won’t fully eject from the chamber after Fring, you’ve got problems. The
usual cause is a faulty stub base deflector tray or damaged chamber extractors.
Inspecting the rounds themselves is also a critical step in flareback prevention.
Rounds that are contaminated with water, oil, or other substances might not
burn completely. The residue left behind could ignite any gases not expelled by the
bore evacuator.
Cam Speed
Instructions for setting the cam based on temperature and operating conditions
start on Page 3-266 of TM 9-2350-264-10-2 (Mar 03), Page 3-160 of TM 9-2350-
288-10-2 (Jul 95) and WP 0518 of TM 9-2350-388-10-3 (±eb 09).
if the deflector tray is
misaligned, the ejected
stub base hits the front
edge of the tray.
eyeball the deflector
tray for dents, nicks, or
gouges, especially at the
front leading edge.
make sure
you inspect
the chamber
extractors for
damage, too.
an extractor
with rounded or
damaged edges
has a hard time
extracting the
stub base.
Check deflector tray for damage
Chamber extractors rounded? Report it!
closely inspect
your rounds
for damage or
contamination
that could lead
to flareback.
rounds that
are in good
condition can
minimize the
severity if a
flareback does
happen.
the best way to reduce
flareback during operation
is to set the operating cam
speed to the s position.
however, if the cam setting is too slow,
the stub base won’t eject properly
and the bore evacuator will start to
discharge before the breech opens.
Inspect rounds for
contamination
before Fring
Set cam speed as close to S as possible
if you find damage to
the deflector tray or
extractors, notify your
mechanic immediately.
They must be repaired
or replaced before
the tank can fire live
rounds again.
A misaligned stub base deflector tray
can also damage the round during load-
ing. The damage isn’t usually noticed since
it happens when the round is chambered.
in addition
to crew PMCS,
sustainment
maintenance is
also critical.
Proper bore-
scoping, recoil
exercises and
the right cable
adjustment
for the gun
system are
critical if the
weapons system
is to function
properly.
682.04-05.indd
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8/3/09
2:54:15 PM
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