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Posted: 11/29/2010 6:15:11 AM EDT
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I've been having an issue with my AR recently that I wanted a second opinion on. For the past about 6 magazines the last round has failed to chamber properly. The first time it happened the last round popped out of the magazine but the bolt held back. Every subsequent time the last round only chambers partially and I have to hit the bolt release to seat it the rest of the way. It's happening every time now, very reliably, and it's always the last round. This leads me to believe that the problem is with the follower spring in the magazine, but I was wondering if others had other ideas. Thanks.
––Surgery |
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That leads me to believe there is some kind of roughness on the follower. Something in the mag is grabbing onto the round and not letting it free.
It doesn't sound like a spring issue. What kind of mags are these and is it just one mag or every mag u have? Edit: I just re-read your post. Are u saying that the bolt is getting caught by the bolt catch/bolt release? I'm assuming that everything is in the right place, meaning, the round is in front of the bolt not under it, and the round has completely left the magazine and is correctly positioned to enter the chamber. |
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Pretty much what you said in your edit. The first time it happened (which now thinking about it may be a separate problem) the round was rattling around lose in the receiver, completely free of the magazine, and the bolt was locked back. Every other time the round has been partially seated in the chamber, with the bolt locked back.
The magazines are Circle Kay 20 rd. I've only been able to test one. Thinking about it more, it does sound like something is cause the bolt to lock prematurely, though I don't know what would cause the last round to partially seat, or even leave the magazine at all, I thought the bolt stripped a round off the top when it slammed forward. Either way, this magazine is pretty old, so I think I'll rebuild it anyways, and maybe take the AR apart and put it back together just for good measure. edit: "Circle Kay", not "Circle K". I didn't get them at a convenience store, haha. |
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Maybe the last rounds are for some reason just hopping out of the mag. If they hop out of the mag as the bolt is traveling rearward or just coming to a stop, then it would reveal the follower too early and trip the bolt catch.
So the problem sounds to be the round jumping from the mag prematurely. You could try closing the bolt on a dummy round (or live round if in a safe place). Then insert a mag with one last round in it and pull the bolt back as fast as possible (trying to mimic operating speed) and keeping the bolt at the rearward position. If the last round keeps jumping from the mag, then there is your problem. I've never heard of or seen this happen and the only way I would see it happen is if the feed lip is not holding the round in. Although I would expect every round to jump out in that case. Of course you could just have a set of over-anxious ammo. 
Are you sure that the bolt is getting caught by the catch and not caught directly by the mag follower? |
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Hm, I'll try those things. Unfortunately I won't be able to for a few weeks as I left the gun at my folk's place. Maybe I'll call my dad and ask him to do it if I pay for dummies.
I would think that if the bolt was getting caught on the follower that pressing the bolt release wouldn't do anything, right? I'm going to find my other magazines and check them out when I get my gun back. Two are old mags bought at a gun show, so wouldn't really be surprised if they were somehow starting to fail, but the third is a factory new from S&W, I hope the problem doesn't occur with that one too. Thanks for the ideas, I'll post back in a while when I get some more results. |
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I have a 5round mag that dose the same. I havent figured out why it is doing it. I agree the round is leaving the feed lips early and letting the blt catch do its job. I am thinking that the feed lips have spread apart and that may be what is causeing the problem. I am going to measure them later tonight and see what I come up with.
MAHA |
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