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Thread: Bolt not locking to rear

  1. #11
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    When you say this is the "second time my gun has done this". Do you mean that it actually has failed to lock back two different times?

    On a gun that works, the number one cause for a failure to lock the BCG back to be mag related.

    Does it happen with a particular magazine(s)? If I get a failure to lockback, I immediately mark the mag, then try 2-rnds to see if it happens again. If it does, I clean the mag, then try 2-rnds again. Third time to fail, I mark it as a Range Mag and never count on it again.

    Again, on a gun that works, the next place to look is the ammo.
    Did it happen with other ammo you have used. Some of the WM 100-rnd packs are 50g bullets. Does it work OK with heavier ammo?

    If this doesn't narrow the cause down, then I'd look at springs and the gas system but I'd be surprised if it is not a mag or the ammo, especially if the gun generally "works".
    Last edited by ucrt; 07-07-10 at 13:37.

  2. #12
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    The gun fires and cycles properly. The only thing not.functioning seems to be the bolt locking to the rear after the last round in a mag. I doubt its a mag or ammo problem as I was using a couple types of ammo and it occurred with 8 different pmags. I could see a problem with one but all 8 at the same time seems unlikely.

    By "second time" I mean that the gun had the same problem a few months back. Many different occasions the bolt would not hold open on an empty mag. I sent it off to be repaired, got it back and.the.problem was fixed.

    Sorry for.all the weird periods. Autotype on my cell phone.

    As far as it being dirty or obstructed, I doubt it. I break down and meticulously clean all my guns every three weeks regardless of hoe.much I've shot them. I hadn't shot the.rifle in between the last two cleanings though. It may sound silly but could not firing it be bad? Obviously a lack of.shooting is bad for.me, but I'm talking about something regarding the workings of the gun. Should I be cleaning it less, I guess?

    Y'all thanks so much for the.help. I wish I hadhalf the knowledge and experience most of y'all do.
    Last edited by mnoe82; 07-07-10 at 15:34.

  3. #13
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    was the problem "fixed" with the same ammo or something else (say 5.56) ?

    Hopefully you have an H buffer and can just downgrade to a standard carbine

  4. #14
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    Well its kind if hard to say.

    I bought a case of pmc at a gun show and was running that when it happened the first time. I still had some left over, already loaded in.mags. we were shooting that as well as the Walmart federal. However it was happening with all my mags, which would have been loaded with some of each. I mean, a mag of pmc and a mag of federal.

    Hopefully its something that will be fixable. The gun has a lifetime warranty on parts and labor. I'm less concerned about that than I am it becoming a larger problem if I need it in a dangerous situation.

  5. #15
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    Here is what I would do, in no particular order.

    1. Contact this company- I went to their website and found very little info. Ask them what size gas port your rifle has. I have a feeling that they are going to stall you or not give you a straight answer.

    2. Check the things we have told you to check. Gas block, FSB, etc... for gas leakage. Make sure that the bolt carrier key is tight and the screws are staked. Also, check your gas rings and make sure they are tight.

    3. My guess is that you have a standard buffer. This can be identified by looking at the face of the buffer. It will either be plain, or have an "H", "H2", etc...I would get an "H" buffer.

    4. Try and get some true 5.56 (not .223) ammo and then take all of it to the range. Load all of your mags with one round only and shoot them. See if the bolt locks back. Make sure that your BCG is wet. Not just a few drops of oil.

    Some other things you may want to find out are whether or not you have an auto BCG or a semi-auto or one of the other variants.

    Quote Originally Posted by mnoe82 View Post
    Well its kind if hard to say.

    I bought a case of pmc at a gun show and was running that when it happened the first time. I still had some left over, already loaded in.mags. we were shooting that as well as the Walmart federal. However it was happening with all my mags, which would have been loaded with some of each. I mean, a mag of pmc and a mag of federal.

    Hopefully its something that will be fixable. The gun has a lifetime warranty on parts and labor. I'm less concerned about that than I am it becoming a larger problem if I need it in a dangerous situation.



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  6. #16
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    Quote Originally Posted by Iraqgunz View Post
    Successful tips for solving problem.

    1. What is the make and model of the weapon?

    2. What type of buffer and spring do you have?

    3. What type of ammo were you using?

    4. What type of magazines?
    what would be a good buffer and spring to get?? i think i just have a generic one...Thanx

  7. #17
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    Another thing to check is a stiff/rough operating bolt catch. I've had to trim a few bolt catch springs due to excessive tension. It really doesn't take much.

    Excessive bolt speed is something that gave me a problem before when combined with a stiff bolt catch. The bolt would outrun the mag follower and not lock back.

  8. #18
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    I experienced the bolt not locking back on the last round due to weak springs. You can test this by putting one round on each of your magazines, shoot them all, and note down which magazines caused the bolt not to lock back. I did this test and found 3 bad magazines that I owned. They were 10/30 Pmags.. go figure.

  9. #19
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    I absolutely concur with Iraqgunz.
    The only thing I would do to speed up the process is to find some NATO pressure ammo (Fed XM193 or M855 is the easiest route) and do a mag-check as explained by a few posters above.

    Some pics of critical parts of the gun may also help:
    Close up of gas block
    Close up of carrier key
    Face of buffer
    Side profile of bolt carrier group
    Bolt/gas rings
    Bolt catch with empty magazine inserted with the upper removed (the actual catch, not the bolt release)
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  10. #20
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    As you can see, there's a lot of possible causes.

    Another one I experienced was a broken gas key bolt. The front bolt snapped, but you couldn't really tell. The head was tightly staked in and the rear held the key tight. But there was a gap under the key that leaked gas.

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