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Thread: Fail To Feed/Double Feed? Magazine Problem or Something Else?

  1. #11
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    Quote Originally Posted by joeg26er View Post
    The upper is a 2A billet, 2A rail, Spikes 11.5, 2a Ti gas block, Radian Raptor charging handle so should not be an issue with the parts. Everything is torqued to spec.
    lower is San Tan billet ambi, Stag LPC + POF trigger. Standard carbine spring and buffer. Tailhook mod 2.

    Each time using a totally different Bolt and Carrier group.

    I got hung up on using just the OKAY 20 rounders so will have to try to use the anti-tilt CProducts 30 rounders next range session.

    This is a new build and now that I think more clearly about it, I am a bit more certain it's the 20rounders that have been giving me issues that I was ascribing to the BCG.

    The casing is ejected, the next round is jammed tip up and with the bolt denting it about midway.
    Does it happen when hand cycling? Slow and fast, or one or the other?
    Moving it slowly, the bolt should catch the back of the rim, as shown inyour last pic. At this point, the bolt will push the round into the chamber. Can you post pic of feed ramps?

    Try new mag,
    Then try h2 buffer with the same 20rd mags, if problem doesnt show when hand cycling.

  2. #12
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    The pics are from hand cycling
    Quickly Pulling charging handle all the way back and crisp release

  3. #13
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    Is there a lip on the feed ramps? It looks like the round is getting stuck there.
    Does the barrel have m4 feed ramps?

  4. #14
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    Barrel is SPIKES BBL 5.56 11.5" FN CHF M4 EXT (SPKSB51106-LW)

  5. #15
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    It will be difficult to help troubleshoot the problem until a lock back check has been performed.

    In the meantime, see how the rifle feeds when letting the BCG go using the bolt release. My initial guess is your recoil spring needs to be replaced. Judging from your description of the problem, it's possible your AR also has a weak extractor spring.
    Quote Originally Posted by sinister View Post
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  6. #16
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    Thanks
    This issue occurs with multiple different brand new bcgs

    So I don’t think it’s related to the extractor spring

    It also occurred with a brand new carbine buffer springs and a new sprinco red
    It will lock back on last round on magazines

  7. #17
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    IIRC, your pictures indicate this occurring with the round feeding from the right side of the mag. Is this the same case in all the malfunctions?

    Assuming the rifle has been supported with the same firmness throughout your experiences, locking back to the rear seems to indicate you are getting enough gas to ensure the bolt head is picking up the round.

    If the bolt head, and not the bolt carrier is picking up the round, the easiest way for you to get the dented brass you describe, is for the round to be kicked upward, into the top of the chamber during feeding - often this is a feed ramp issue.

    Since you have M4 feed ramps I'd check to ensure that the M4 cuts in the upper blend nicely with the M4 extension.

    I would also go with an H or H2 buffer.
    "If I had asked people what they wanted, they would have said a faster horse." - Henry Ford

    “You are responsible for your actions, but the world doesn’t turn around you, so it’s important that you find something bigger than yourself to work for, a way for you to make a difference.” - Drew Dix, MOH VN '68

  8. #18
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    I had some time to check the M4 cuts in the upper

    I found the transition from the cuts to the barrel extension is NOT smooth. The receiver ramp is approx .5 mm lower than the barrel ramps. So the bullet tip is forced to overcome a .5mm step
    I am thinking this is causing the failures to feed and rounds getting smashed in the middle ?

    I never thought to check that given the high end billet construction of the upper
    I compared the m4 cuts/barrel extension transition of this upper to my Larue and a PWS and those others have very smooth and well fit transitions.

  9. #19
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    Do us a favor and let us know how it works out when you get the feed ramps matched up/

    Thanks!
    "If I had asked people what they wanted, they would have said a faster horse." - Henry Ford

    “You are responsible for your actions, but the world doesn’t turn around you, so it’s important that you find something bigger than yourself to work for, a way for you to make a difference.” - Drew Dix, MOH VN '68

  10. #20
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    Quote Originally Posted by MistWolf View Post
    It will be difficult to help troubleshoot the problem until a lock back check has been performed.

    In the meantime, see how the rifle feeds when letting the BCG go using the bolt release. My initial guess is your recoil spring needs to be replaced. Judging from your description of the problem, it's possible your AR also has a weak extractor spring.
    When you fire one round, just one round in the magazine, does the bolt lock back? Make just one change at a time to isolate the problem.

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