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12/24/2013 10:50:38 AM EDT
Ok guys this isn't my first build by a long shot but it is the first time i've had this problem. I just built my first ar pistol and when i took it to the range it was jamming (spent casing wouldn't extract properly while the new round would also get stuck half way into the chamber). I figured the pistol might be short stroking so continued to run through some ammo with varying results. I had a think about it and remembered that the bolt seemed stiff when i was charging the weapon (plenty of lube btw so it seemed odd).

Anyway on a whim i threw a new bcg in it and ran 500 rounds through it without a stoppage. I stripped down the first bcg and checked everything the bolt and extractor/pin seem fine, as does everything else. Everything seems to function fine, out of the weapon, so i can't figure out what's wrong it's almost as if the carrier itself is slightly too wide or out of spec. This is a new bcg i've had sitting in my drawer for 2 years and i went over it with a fine tooth comb before using it. It seemed tight in the upper compared to my others but still i can't figure it out.

Any thoughts are appreciated.
12/24/2013 12:46:27 PM EDT
[#1]
Try the new bolt in the old carrier that ran 500 rounds...
That'll tell you if it's the carrier.

Since it was stripping rounds from the mag, doesn't sound like it was short stroking much.  But still check the little things like gas ring condition and alignment, internal lube.

Are there any differences between the carrier that ran and the one that didn't? (Like shrouded vs unshrouded, brands, etc)
12/24/2013 12:47:58 PM EDT
[#2]
the one that worked was a colt. the one that didn't i got from midway a few years back and to be honest i forget what brand it was. You're right though i will just swap out parts as i go until i get a failure and see what happens.
12/24/2013 5:05:46 PM EDT
[#3]
As stated, swap the bolts on the working B/C and the new B/C, and retest again with these combo's.

Either the new bolt is out of spec and head spacing too tight,

Or the new carrrier key is too wide for the upper receiver and binding in the track (sides may need to be lapped) / the key is leaking against the top of the carrier ( you may have to pull the key and lap it into the top of the carrier to correct the leak).


Also with both carriers with key bolt-less, dry fit them into the receiver to check for key binding in the track/ gas tube not aligned with the key.
12/24/2013 7:54:02 PM EDT
[#4]
Going to say out of spec bolt.....I had a similer problem a while back bolt lugs were a c hair to big.
12/25/2013 9:35:06 AM EDT
[#5]
Quote History
Quoted:

Or the new carrrier key is too wide for the upper receiver and binding in the track (sides may need to be lapped) / the key is leaking against the top of the carrier ( you may have to pull the key and lap it into the top of the carrier to correct the leak).
View Quote


It looks like this might be right but can't get much range time today as i'm fixing turkey will have to check more thoroughly over the weekend.
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