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  1. #1
    Join Date
    Sep 2009
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    Default Blown primer found itís way into trigger mechanism: question.

    I just got back from the range where I had a malfunction that I initially couldnít diagnose. After about a magazine and a half through my .300, the trigger went dead. I unloaded the rifle, pulled it apart, and looked at everything. Couldnít see anything wrong. Being cautious, I decided to pack up and head home, where I could take a proper look at everything. Looking into the lower receiver, I found the problem: a primer had blown out of one of the cases upon firing, and lodged in the trigger mechanism, binding it up. I removed it with a dental pick, and rifle is fine again. But now I have concerns.

    Iíve heard of this malfunction before, including a more severe variant where the primer gets between the carrier gas key and charging handle, requiring disassembly of the stock and buffer tube to fix.

    What are the chances of this happening again, and is there any way to prevent it, short of careful ammo selection? On the range is no big deal, but it would be a real mood killer in a fight.

    Ammo in question was Fiocchi 125g SST. Iíve fired about 800 rounds of it through this particular weapon so far, with no problems, until this happened. Was this just a fluke that could have happened with any ammo?
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  2. #2
    Join Date
    Nov 2018
    Posts
    805
    I've heard of this happening with other brands as well. Seems that it occurs when the primer is overcharged or the powder is overcharged, or if the primer isn't seated properly. Sounds like a manufacturing fluke to me. But someone else may know more and be able to give you some other advice. I wouldn't worry about it overmuch, although you're right, it would be a "mood killer" in a fight, to be sure.

  3. #3
    Join Date
    Mar 2012
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    I've only seen this happen with reloads, though I'm sure it's not exclusive to them. Best ways to mitigate this happening in a gun fight would be to use quality ammunition and, if you really need that extra level of assurance, to have your primers crimped. Obviously, assuming your rifle is good to go, this is a very rare occurrence, so I wouldn't sweat it.

    That said, besides the ammo being bad, another reason this could happen is excessive headspace. How do your fired casings look? Any bulged or pierced primers? Cratering or ejector swipe?
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  4. #4
    Join Date
    May 2006
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    NWFL
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    16,498
    Really sounds like a loose primer. I am guessing that it is falling out of the case more than being blown out unless the AR action has residual gas pressure at the time of of unlocking that I doubt. Military 5.56 primers are routinely crimped. It seems that since I do plan to reload the 300 blackout I will have to look into how a primer can be crimped for ammo that is meant for important purposes. This not the first time I have read of this with the AR15 action.
    EDIT
    Does that weapon have a suppressor on it? That could cause some residual gas pressure.
    Last edited by barnetmill; 07-10-2021 at 02:42 PM.

  5. #5
    I've had this happen once with Hornady 55gr HP match bulk ammo. It can happen. Good thing it was during a rifle match, that ammo is now relegated to that purpose.

  6. #6
    Join Date
    Aug 2014
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    4,882
    Anyone heard of this happening with mil-spec crimped primers?
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  7. #7
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    Primary reason to carry a pistol at all times. And for using Mil Spec quality ammo.
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  8. #8
    Join Date
    Mar 2012
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    Georgia
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    Quote Originally Posted by extremist View Post
    I've had this happen once with Hornady 55gr HP match bulk ammo. It can happen. Good thing it was during a rifle match, that ammo is now relegated to that purpose.
    Let me guess, was it Hornady Frontier?
    "If you believe what you like in the gospels, and reject what you don't like, it is not the gospel you believe, but yourself." ó Augustine

    "That upon which you set your heart and put your trust is your god." ó Martin Luther

  9. #9
    Join Date
    May 2006
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    NWFL
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    Are there mil spec 300 blackout loads with a crimped primer?

    If one reloads maybe do it with a hand operated priming tool that can you feel how much pressure you are using and reject those rounds that require less effort for seating.
    An out of spec factory round with a soft head could expand enough to drop a primer, but I am not sure how that would happen.

  10. #10
    Join Date
    Feb 2009
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    Colorado
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    All my hornady Black VMax loads are crimped.

    I'm not really worried about primers coming out even with my handloads though. For other ammo I'm not really either. For all the ton and tons of rounds that get fired all the time and the handful of times I have heard about it it seems statistically insignificant.
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