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4/12/2009 5:20:45 PM EDT
My buddy just bought a Stag upper but when he put a magpul Pmag into his rifle, the bolt wouldn't release unless he "jiggled" the magazine. When the bolt was closed and he inserted the Pmag, the charging handle wouldn't come back unless the magazine was "jiggled." What causes that? Is there something wrong with the upper?

Once he got the bolt to go forward, the rifle performed just fine.
4/12/2009 5:22:19 PM EDT
[#1]
Is it only with that one mag type, or does it happen with GI mags also?
4/12/2009 5:26:06 PM EDT
[#2]
Not to sound obvious, but when you inserted the mag, was it empty?  And if it was empty, did you press the bolt catch/release?
4/12/2009 5:52:23 PM EDT
[#3]
The problem occured with a full mag.  It seems the mag is pushing the bolt catch up and preventing it from releasing the bolt.  Even when you push the bolt catch release, the bolt won't go forward without jiggling the magazine.

4/12/2009 6:11:11 PM EDT
[#4]
When you insert the mag, and pull the charging handle back, when it gets stuck, look inside the chamber and see if you can see what is snagging the bolt catch.

There are a few possible reasons this is happening:  the pmag is out of spec, and seats the rounds too far to the rear, causing the rounds to snag the bolt catch.

Or, the bolt catch lip is too long, engaging the rounds.

Or, the little recess on the rear of the mag where the bolt catch is supposed to intersect is not in spec (its too high), and the rear portion of the mag pushes the catch upwards.

All these problems can be solved either by replacing the mag, or using a file.

4/12/2009 6:11:24 PM EDT
[#5]
Problem diagnosed -

The bolt catch is slightly over-sized and it is hanging up on the edge of the Pmag.  We have the same lower but the LPKs were different (mine is RR and his is Stag) and you can SEE that his bolt catch is longer than mine where it hangs up on the magazine, keeping it from being able to move downward to release the bolt.

So, we're going to file it down slightly (in the front) to allow the bolt catch to clear the magazine  when the release button is pressed and get him another bolt catch (Rock River FOR SURE!) ASAP.

Thanks for the input guys!
4/13/2009 10:33:07 AM EDT
[#6]
Glad to be of service :)
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