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Thread: PMC X-TAC 55gr, a bit on the spicy side.

  1. #11
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    Looks like a case head failure due to thin/low web at first glance.
    Jack Leuba
    Director of Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  2. #12
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    Quote Originally Posted by markm View Post
    I don't know about PMC's stuff. I'd guess it's a ball powder. Depends on the burn rate of the powder and how much could be in there. We shot the overcharged AAC ammo that's actually a compressed load, it didn't blow up any guns. I'm guessing AAC's powder is a slower burn, because if it was that overcharged and fast powder, it'd have at least ruptured a case head.

    But to the points made, if the damage is that bad, you would be worried about an obstruction or something.
    Something fast, like H322 or H4198, would have some room left in the case for an overcharge, but I'm not sure it would be able to generate enough pressure for a kaboom.

    Sometimes I wonder if the manufacturer was loading pistol rounds and didn't get it all that fast burning powder cleared out of the hopper before running the rifle rounds.

    PMC has a really good reputation but I've seen a lot of turnover in manufacturing since the pandemic.

  3. #13
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    Quote Originally Posted by Failure2Stop View Post
    Looks like a case head failure due to thin/low web at first glance.
    I would not have guessed that would cause so much damage without overpressure. How does the bottom of the carrier get torn off?

  4. #14
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    The more kaboomed ARs I see, the more I think Mr. Stoner was a genius. No harm to shooter, which seems typical for the platform.

    Andy

  5. #15
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    Quote Originally Posted by Disciple View Post
    I would not have guessed that would cause so much damage without overpressure. How does the bottom of the carrier get torn off?
    55kpsi (.223) is a significant amount of pressure, and the X-Tac is probably north of that given the velocity increase of it over the bronze line.
    When the case head/web fails it's happening during that high pressure time.
    The web separates, usually starting at the extractor slot, as that's where the head has no support, and the pressure then follows the path of least resistance.

    This observation is based on experience and a few investigations that involved ammunition manufacturers' feedback.
    A detailed in-person evaluation would be needed to have a high degree of certainty of either failure event, but that looks a lot like a case head failure/separation at web.
    Jack Leuba
    Director of Sales
    Knight's Armament Company
    jleuba@knightarmco.com

  6. #16
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    Thank you. An impressive reminder of the power that small piece of brass normally controls.

  7. #17
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    Quote Originally Posted by markm View Post
    Ammo quality has suffered recently.
    Kinda seems to run in a 5-7yr cycle... if not one manufacturer, it is another.

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