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Posted: 5/13/2010 11:00:48 AM EDT
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I have a build that a friend and I assembled
18" barrel, rifle gas system When magazine inserted from opened bolt it usually will not strip a round when the bolt is dropped unless I use the charging handle Extraction is fine and bolt locks back when single round is fired I get a few failures to feed from every magazine. Sometimes a partial feed sometimes no feed upper and lower are Spikes, BCG is STAG. gas block is MI. Barrel is Superior Barrels Everything feels smooth and no unusual wear. I have a few hundred down the pipe. Any ideas ? |
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Bolt locking back on the bolt catch after the last shot means that everything is clean with the stoke, so the problem is not there.
Now when you have problems with the charge (either releasing the bolt catch, or pulling back on the charging handle and letting go of it, and not trying to walk the charging handle back down), exactly what happens? Is the tip of the bullet just inside the barrel extension with the bolt locked up, the bullet tip striking the upper receiver under the barrel extension ramp (will be tell tail signs of such if you look), the bottom of the mag feed lips so burred that is digging into the brass, or the mag spring the wrong length or too weak for the receiver extension in play (read full length stock spring should be around 11.75", while a telescoping butt stock spring 10.5". Barring the spring being the correct length/strength, the mag catch threads flush with the face of the mag release button and retaining the mags correctly, the mags in working order with any feed lips burs cleaning up, could be that the hammer is catching the firing pin collar on the forward movement, and the reason that the Bolt is locked up and even the Forward assist will not move it any forward. Go over the problem mentioned here, and if it does turn out to be the hammer and firing pin, then I can post the tweak to correct such. |
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When I charge using the handle (never walked) it strips a round and chambers. Sometimes the gun will not strip a round at all from the magazine when cycling. I have less issues with a partial feed. About 1-2 rounds out of every other magazine will have a partial feed on the shoulder of the round with the bolt not going into battery. When it does decide to cycle everything is good. I can sometimes get it to feed 8-12 rounds without a failure.
I've been using GI magazines and Brownells magazines. Problem persists no matter the magazine. P mags seem to be worse Ammunition has all been M855 62 grain. Springs are good (new) from STAG as is the buffer. The Tube is also from STAG |
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Ok, it is either coming down to the ejection side of the bolt catch tagging the carrier when it is suposed to be down, or the mags/followers are having a problem.
On the bolt catch, take a good look at the back ejection side edge of it. Does is appear that the carrier has been tagging/catching it, causing the B/C to slow down. If so, might want to go back and check the bolt catch install, and even maybe round that right edge so it will no longer catch the carrier when it's down. On the mags, pull then apart and give them a good CLP cleaning. Also, try using a wooden ruler and shove the follower all the way down, and let it snap back up. The follower should come up cleanly, without any kind of binding on the inside of the mag. If you get binding, pull the follower and clean up any skirt edge that is causing the drag. On the mag catch, with the bolt locked home, insert a mag into the well with either the catch removed, or the button all the way in. You want to push mag body alone all the way up until it kisses the bottom of the carrier, then see how far down it will drop as the catch goes to retain it. The free play you are looking for should be in the 1/8" range, and if you fine more, might be time to try another catch to see if the one you have is defective (catch lip milled too low on the one you have). Between the two, I would say that either the mag is not recovering in time for a clean strip (follower binding), or the mag is being retained too low in the mag well for a clean strip during charging. The fact that either the round is being nose shoved into the front of the mag, or the bolt missing the rim of the mag and grabbing it by the middle of the case, it's all a mag related problem so narrow your search to the problem there. Again, the bolt is locking back cleanly, so you can forget all about any gas/cycle area's and now is is coming down to a clean mag/round strip with your attention directed there. |
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