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Thread: Keyholing after pin and weld mb556k

  1. #11
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    Took it back and he said that there were no baffle strikes. He also rechecked and measured to make sure it was aligned properly and it was. He told me that he had seen this one other time and it was in a LaRue stealth upper. The LaRue upper apparently didn't like m855 but would shoot anything else from 55 all the way to 80gr. Then he told me there might be an issue with the batch of ammo and qc on m855 wasn't that great...

    It is a reputable shop

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  2. #12
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    Have you actually fired different types of ammo to see if there is a change, that would be a good starting point. I would definitely use something other than that American Eagle.
    Last edited by PaLEOjd; 01-26-16 at 14:39.

  3. #13
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    I was going to say try different ammo.

  4. #14
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    It's a mix of ae m855 and winchester m855 going to the range with some winchester 193

    Just ran some winchester 193 and there was still keyholing

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  5. #15
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    I think somebody owes you a barrel.

    Just too make sure though I would do your due diligence with more than just m855 and 193 from one or two manufactures. Also what range does the key holing start? Can you make it happen at 25m?
    Last edited by turnburglar; 01-26-16 at 19:24.
    "Just throw Krylon on it"

  6. #16
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    Pmc,ae and winchester m855
    independent, ae, winchester and pmc 193 has been tried

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  7. #17
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    Quote Originally Posted by mean_gene View Post
    A little carbon build up but I can't really get to it.

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    It looks like a giant mountain of carbon on the left, and very little on the right. That might be enough to induce keyholing or at least accuracy issues, but it is hard to say if that is what is happening here. I guess the best way to clean (due to perm'd muzzle device) would be a long soak in an ultrasonic tank. Who knows if that will solve the keyholing issue.

    I also wonder what torque value your old flash hider was installed at, what torque the new one was installed at, and how aggressive of a weld the smith put on that thing. Pinning a MB should only take a 1 second zap of the TIG, not much heat at all. Perhaps your barrel was nearly about to keyhole, and then one of the above issues was the last straw.
    Last edited by P2000; 01-26-16 at 20:55.

  8. #18
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    p2000 this was taken nothing but 20 min ago

    No cleaning was done just click on a q tip for contrast

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  9. #19
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    Quote Originally Posted by mean_gene View Post
    p2000 this was taken nothing but 20 min ago

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    That looks not as bad and more symmetrical. Was the accuracy good prior to the muzzle swap?

  10. #20
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    Could cover a 5 shot group with a half dollar at 100

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