PS Magazine - TB 43-PS-681

PS, The Preventative Maintenance Monthly

ISSUE 681

AUGUST 2009
PS Magazine - TB 43-PS-681 - Page 12 of 33
20
PS 681
AUG 09
21
PS 681
AUG 09
S
ome bad M249 machine
gun
extractor
pins
have
gotten into the Army supply
system. They need to be
extracted ASAP.
A bad extractor pin can
break or back out of the
bolt, causing the M249 to
stop Fring. If an extractor
pin
fails
while
the
bolt
is
locking
in
place,
the
bolt can jam in the barrel
extension, which prevents
the Fring pin from striking
the primer. That could lead
to a cook-off. If the pin fails
while the bolt is unlocking,
the spent cartridge won’t
be extracted.
Unless your M249s are
new or have just come from
overhaul at Anniston Depot,
their extractor pins, NSN
should
be replaced. All extractor
pins in gun extractor parts
should also be replaced.
I
n PS 675 (±eb 09), we told you how to make sure your M240 machine gun’s sear
was still in good enough shape for safe Fring. But an important guideline was left out
that is causing M240s to flunk the test.
Here’s the check: After clearing your M240, move the safety to
F
(Fre) and pull the
cocking handle completely to the rear to lock back the bolt. Then return the cocking
handle to the forward locked position. Place the safety in the
S
(safe) position and
depress the trigger. Nothing should happen.
Next move the safety to
F
and hold the cocking handle to the rear while you fully
depress the trigger. Then ease the bolt forward until it locks. You should not be able
to move the safety to
S
.
Here’s the important guideline:
If the trigger is not fully depressed and held
there while easing the bolt fully forward to the locked position, the weapon will
fail this test even if the sear is good.
If your M240 does flunk this test, it shouldn’t be Fred. Your Feld repairman needs
to check it out.
The reason sears wear out fast is because gunners don’t pull the trigger fully to the
rear when Fring and don’t release the trigger fully when they’re Fnished Fring. So
remember to pull the trigger completely back to keep the sear healthy. It also helps
the sear to store your M240 with the safety on
F
and the bolt locked forward.
But you don’t need to stop Fring your M249s until
the new extractor pins arrive. What you do need to
do is check the extractor pin before Fring, during
PMCS and maintenance, and every 500-1,000
rounds. The extractor pin should be countersunk to
the depth shown here:
If the pin seems to be working out, don’t Fre the
M249 until you get the pin replaced.
±or more information, see TACOM LCMC GPA
09-011:
tacom_wn/gpa09-011.html
M249 Machine Gun…
ExtraCt Bad ExtraCtor Pins
M240-Series Machine Gun…
Sear
Safety
Check
Part II
uh-oh,
I’m
jammed up.
I’ve got a bad
extractor pin.
no more firing
until you get a
new one.
If extractor pin is
not
countersunk to this depth, don’t
Fre your M249 until pin is replaced
CORRECT
REPLACE
You must fully depress trigger while easing bolt forward to locked position
Otherwise, your M240 may flunk test
even if its sear is good
I’m sorry,
but you
flunked the
sear test.
what do you
mean
flunked?
my sear is fine.
you
didn’t
fully depress
the trigger when
you moved my
bolt forward.
that’s
why
I flunked
the test.
681.20-21.indd
1-2
7/7/09
3:05:01 PM
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