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Thread: A bit of help with this malfunction.

  1. #11
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    Quote Originally Posted by Redhat View Post
    You might also check your carrier key and gas tube
    For what?

  2. #12
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    Quote Originally Posted by Clint View Post
    The first thing to do is check for lockback on single rounds.
    ALWAYS
    <for those playing along at home>

  3. #13
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    Quote Originally Posted by Redhat View Post
    You might also check your carrier key and gas tube
    Quote Originally Posted by Wiggity View Post
    For what?
    For gas leakage. If the ammo was working before, it sounds like something changed.

    From reading the description of the malfunction, it sounds like the bolt is traveling rearward enough to eject the spent casing but not enough to catch the rim of the round in the mag. The bolt, as it returns forward, catches the case body to push it out of the magazine. Since the case is under the bolt, it cannot be fed into the chamber

    Just to repeat the above- ALWAYS check to be sure the bolt will lock back with a single round in the magazine
    Last edited by MistWolf; 12-16-11 at 00:04.
    INSIDE PLAN OF BOX
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    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
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    5. HA-HA!!

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  4. #14
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    My 11.5" and 12.5" both have eaten up the PMC Bronze Line with no issues. I fired about 600 rounds of it during the Magpul Dynamic Course.

    For shits and giggles use a heavier buffer and see what happens. I would also do the lockback test as Tweak mentioned. As a matter of fact that should be one of the first things to check.



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  5. #15
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    OP

    If it helps you any, I went through the same issues with my SBR.

    Couple things I did for trouble shooting...

    4 rounds loaded into each mag:
    For me, this gives a bit of insight into the extracting, ejecting, loading, locking action of the rifle.

    1 round loaded into each mag:
    Checking to make sure the rifle is locking back on an empty mag, not enough gas, too much gas...

    Changed followers in magazines:
    I had standard green GI followers and switched to Magpul followers. I had good results with those.

    Buffer change:
    I started with a carbine buffer (Standard carbine spring) and worked my way up to an H3 buffer.

    Gas port:
    In the end (For my situation) my GP was too small.

    Maybe some of this will help you. The guys here that helped me were pretty spot on with their advice and additional trouble shooting.

  6. #16
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    Quote Originally Posted by nimdabew View Post
    From waht you said, it sounds like the carrier speed is too fast and the magazine spring isn't acting fast enough before the BCG slams home. Do you have an H3 buffer and maybe an extra power spring laying around so you can swap weights around to change the buffer weights?
    This is one of those regurgitated myths that needs to be quietly put to rest.

    The bolt group will NEVER be able to outrun a spec magazines ability to feed the next cartridge.

    Post #6 and #13 both provide valuable information. I believe that you have two issues trying to be diagnosed as one.
    Last edited by MarkG; 12-16-11 at 10:25.

  7. #17
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    Quote Originally Posted by MistWolf View Post
    For gas leakage. If the ammo was working before, it sounds like something changed.

    From reading the description of the malfunction, it sounds like the bolt is traveling rearward enough to eject the spent casing but not enough to catch the rim of the round in the mag. The bolt, as it returns forward, catches the case body to push it out of the magazine. Since the case is under the bolt, it cannot be fed into the chamber

    Just to repeat the above- ALWAYS check to be sure the bolt will lock back with a single round in the magazine
    Yep! If it fails the single round lock open test, this is where I would look.

  8. #18
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    Quote Originally Posted by MK18Pilot View Post

    The bolt group will NEVER be able to outrun a spec magazines ability to feed the next round.
    This is an interesting assertion.

    Can you provide any backup or further explanation?
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  9. #19
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    Quote Originally Posted by Clint View Post
    This is an interesting assertion.

    Can you provide any backup or further explanation?
    The spring in a magazine is under a constant load. As a cartridge is stripped from the magazine and chambered, the next cartridge in the stack is moved up in the magazine and is trapped by the feed lip well before the chambered cartridge can be fired. That is to say that it is "on deck" before the recoil phase of operation begins.

  10. #20
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    The problem isn't the bolt out running the magazine before it can chamber and fire the next round, the problem is raising the round into place before the bolt moves forward to strip it from the magazine.

    As the bolt moves rearward, it pushes the top round down. If the bolt moves forward again before the magazine can raise the round into position, the bolt will pass over it. It may be possible that with a fast bolt and/or weak spring, momentum will carry the rounds down further, exacerbating the problem
    Last edited by MistWolf; 12-16-11 at 14:56.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

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