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Thread: What are the causes of a double feed

  1. #1
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    What are the causes of a double feed

    Ok I'm mystified as to what can cause a double feed. My wife was having them towards the end of the day today. Here is the scenario

    Colt 6920 (the bolt is not colt, but the carrier and everything else is)
    Total shots fired: 146 rounds
    Magazines: US GI 30 and 20 round types
    Shooting positions used: Sitting, prone (both with 20 round magazines) standing (with 30 round magazines)(magazines were never used as a monopod)
    Federal XM193...no problems all day
    Georgia Arms 55gr FMJ - that's when the double feed problems occurred.

    Now I have experienced the same problem when using GA in the past and am inferring that its the GA ammo. My question though is why? What would be wrong with the ammo that would be causing this.

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    Please explain what you mean by double feed. If you mean 2 live rounds attempting to feed at the same time then it is magazine related. More than likely the magazine spring is worn. 20 rd mags aren't know for being the most reliable.



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    "Double-feed" is a very general category.
    A true double feed is a magazine or operator fault where the rifle attempts to feed two live rounds simultanously. Magazine issue is generally spread feed-lips. Operator error is usually slapping the magazine dunring seating, causing a cartridge to pop free of the mag, the other is when a initial make-ready fails to feed/chamber and the user re-cycles the CH with the mis-fed cartridge in the upper.

    You can also have a dropped extraction where the fired cartridge is still in the chamber when the gun cycles, resulting in a live round hitting the base of a fired round in the chamber. This issue is addressed through the well-covered extractor fixes.

    Failure to eject ia also a possibility, where the spent cartridge is still attached to the bolt face when the gun cycles, resulting in the attempt to feed a live and a spent cartridge. Issues with this are ejector/extractor related.
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    Double feed as in two live rounds:

    As already said slamming mag too hard into gun
    Bad magazine




    Double feed as in an empty and a live round caught in upper:

    Short stroking, causes:
    Too weak of ammo, not enough lube, too strong a buffer spring and/or too heavy of a buffer, too much extractor tension, gas leak or running too many CAR 'fixes' as in using a LMT enhanced carrier (the one with the larger expansion chamber) in a gun that it won't work (like a LMT 10" upper).
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    Another cause if a "double-feed" is one where a live round is trying to occupy the same space as a spent cartridge that was not extracted (FTE). Then you have an extractor issue unless the rim of the spent cartridge was ripped off by the extractor. In that case you might have a chamber issue that is causing the case to stick (i.e. Laquer from Wolf ammo, rough chamber, etc.).

    Good luck!!
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    Thank guys. What she experienced was two live rounds trying to be fed at the same time. I did ask her if she was slapping the magazine at all, she said no. I had her demonstrate to me how she was loading the magazines and yeah, shes not slapping them. Ergo why I'm completely baffled. Like I said, this only happened with the GA ammo, not the federal.

  7. #7
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    Quote Originally Posted by HES View Post
    Thank guys. What she experienced was two live rounds trying to be fed at the same time. I did ask her if she was slapping the magazine at all, she said no. I had her demonstrate to me how she was loading the magazines and yeah, shes not slapping them. Ergo why I'm completely baffled. Like I said, this only happened with the GA ammo, not the federal.
    The ammo is sized wrong, weak and/or you have a borderline bad magazine. She could be allowing the gun to move too much have her try a more aggressive stance.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

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    When you say 2 rounds try to feed......

    Do you mean one it going into the chamber and the other gets caught in the upper and jammed into the gas key?

  9. #9
    As stated above; 99% of the time a Double Feed (2 live rounds trying to be chambered at the same time) is a magazine issue.
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    Quote Originally Posted by gotm4 View Post
    The ammo is sized wrong, weak and/or you have a borderline bad magazine. She could be allowing the gun to move too much have her try a more aggressive stance.
    Thanks. Her stance wasn't bad, but it wasn't great either. So that is something I worked with her last night.

    Quote Originally Posted by Low Drag View Post
    When you say 2 rounds try to feed......

    Do you mean one it going into the chamber and the other gets caught in the upper and jammed into the gas key?
    Once round gets partially fed into the chamber, the second one follows it and gets the bullet portion wedged between the bottom of the top round and the top of the chamber / ramp. This is an illustration I just whipped up that shows whats happening.


    Quote Originally Posted by BravoCompanyUSA View Post
    As stated above; 99% of the time a Double Feed (2 live rounds trying to be chambered at the same time) is a magazine issue.
    Normally I'd agree with you but this one has me stumped. Only the one type of ammo double feeds. Its got me scratching my head unless it is the ammo.

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