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Results 1 to 9 of 9

Thread: Case failure

  1. #1
    Join Date
    15th September 2010
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    Case failure

    I was at the range last week and found a 9mm shell casing that was split in half midway between the case head and case mouth. The primer was also backed out quite a ways. What would cause a failure like this, improper headspace? Any other reason? I assume the other half was stuck in the chamber. What a nightmare!

  2. #2
    Join Date
    2nd June 2004
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    Double charge.

    This is why you should never shoot reloads obtained from other people.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
    Likes (1) :
    MuyModesto (23rd November 2018)

    Last edited by Hawkmoon; 30th December 2017 at 15:44.


  3. #3
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    You are right about shooting other people's reloads! Assuming it was fired in a semi auto, would not the primer back out and then re-seat when the case head hit the breech face during its cycle?. Also, I did not notice the primer being flattened or showing any visual signs of excessive pressure. Then again, I am pretty new at this reloading game and refer to you more experienced guys!

  4. #4
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    29th August 2017
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    Quote Originally Posted by .45s r best View Post
    ...
    I assume the other half was stuck in the chamber.
    ...
    Do you mean that the front half was missing altogether?

    Possibly the 9mm cartridge found its way into a non 9mm chamber.

    A 9mm can fire in a .40 S&W for example. The front half of the case usually bulges or splits lengthwise though in that case.

    Maybe a 9mm cartridge in a .357 Sig chamber? Or 38 Super?

    -
    Last edited by megafiddle; 30th December 2017 at 21:21.


  5. #5
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    Yes, the front half was gone. Looked like a reloaders nightmare to me!

  6. #6
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    Possibly fired in the incorrect chamber. Overcharges remove or bulge the back end of the case near the feed ramp cutout. The backed out primer also suggests the primer had room to back out, which further suggests the case was not fired in a chamber it was designed to be fired in. One might have also looked for a bit off center firing pin strike.

    The totality of its appearance somewhat suggests an excessive headspace condition, which again possibly suggests the wrong chamber.

  7. #7
    Join Date
    25th September 2006
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    As 45s r best mentioned, a spent case fired in a normal chamber will have a flush seated primer because while the primer backs out as much as case length and headspace allow, it gets seated flush when pressure causes the case head to contact the breech face. Based on SAAMI specs, a minimum length loaded case (0.744") fired in a maximum headspace chamber (0.776) will see the primer back out 0.032". But the fact that the primer didn't get reseated seems to indicate the pressure didn't get very high - at least not high enough to reseat the primer.

    The separated case would explain the lower pressure, but why it separated in the first place may never be known.

    However, if the case is still available the average OD of its "mouth" - the average of its maximum and minimum OD's - will give a little idea of the ID of the chamber it was fired in. This OD can also be compared to the case OD just at the forward edge of the extraction groove to get a little idea of how high the pressure reached.
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  8. #8
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    17th August 2017
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    Think twice about picking up brass that you did not shoot

  9. #9
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    15th September 2010
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    I should have saved the case to look at later, but I tossed it. I agree with what was said about picking up brass at random. I have picked up brass, but I am pretty carefully with it and look at it closely.

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