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Ruptured Case

Discussion in 'Reloading' started by steve4102, Sep 23, 2011.


  1. steve4102

    steve4102
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    #1 steve4102, Sep 23, 2011
    Last edited: Sep 23, 2011
  2. ColoCG

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    Headspace too long or too much shoulder setback, too much pressure. If it didn't fire the first time the cartridge could have been loose in the chamber because of the headspace problem. Could be all of the above need more info. :dunno:
     

  3. fredj338

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    I am pretty sure the mini can fire out of battery, much like an M1. A high primer or case that isn't sized properly or a bullet that is too long, all would cause the bolt to not quite lock but the firing pin could still set off the primer. It's an educated guess.
     
  4. Colorado4Wheel

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    It was the Glock Fairy.
     
  5. steve4102

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    Thanks Fred. I had a heated discussion about the Mini-30, slamfires and out-of-battery fires a few years ago. I finally went to the source and asked Ruger if the Mini could fire out-of battery.
    This is what they told me.

    "As the bolt closes a protrusion in the aft end of the firing pin catches on the action giving positive retraction and only clears when the bolt rotates and locks.This also makes it impossible to fire untill the bolt is locked."

    So if the Mini-14 can't or should I day shouldn't fire out-of-battery, what else could cause this?

    Thanks
    Steve
     
    #5 steve4102, Sep 23, 2011
    Last edited: Sep 23, 2011
  6. noylj

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    Can you pull the bolt back slightly and dry fire the rifle?
    You can determine how far out of battery it will fire.
    Have you had a gunsmith check the rifle for damage?
    You may want to get a case gage and check your reloads.
     
  7. steve4102

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    Once fired LC brass. FL sized. Trimmed to 1.750. Sierra 65gr SP. 25gr H-4895. Single stage press. Charges weighed and trickled. Fired 120 rounds that day all loaded during the same session. 45 of these rounds were fired after the KB without issues.
     
  8. ColoCG

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    Since it was only "once fired brass" you wouldn't think there would be incipient case head separation. The load is stiff, Hodgdons shows 63gr. Sierra with a max of 25.5gr. H-4895, but not excessive.

    If it couldn't have fired out of battery. Other possibilities could be, what was the oal of the cartridge? It might be possible that the bullet was forced deeper into the case by bolt slamming the cartridge in the chamber twice, causing excessive pressure.

    Or just a weak case.:dunno:

    P.S. Or what noylj said above.
     
    #8 ColoCG, Sep 24, 2011
    Last edited: Sep 24, 2011
  9. WiskyT

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    My two guesses are that it was an overpressure condition. This could have been caused by one or all of the following: overloaded powder charge, lower capacity of milspec brass, short leade, long CAOL causing the bullet to impinge on the rifling. The fact that it failed to fire the first time supports the long COAL idea since the breach may not have closed all the way the first time, preventing firing.

    The second and less likely guess is that the piece of brass was defective.
     
  10. steve4102

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    Thanks.
    Overload, maybe, but if it was just an overload, why the failure to chamber on first attempt?

    Long OAL maybe, but the Mini-14 is a 5.56 with a long throat. If the offending round was long enough to get the bullet pig-jammed into the lands then it would not fit into the mag. This and all rounds that day were mag fed.
     
  11. WiskyT

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    Yeah, I can make arguements against my guesses. An overload? How much of that powder will actually fit in a case? Maybe enough to flatten primers, to cause stiff or impossible extraction, but can you fit enough of that powder to split a case head?:dunno:

    Short leade or too long bullet seating usually results in the bullet sicking in the rifling and it gets pulled from the case if a live round is ejected, like it was in this case:dunno:
     
  12. steve4102

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    How about this? Is it possible to size a case to much pushing the shoulder back to far allowing excessive headspace. This excess headspace caused the first round misfire? When the second attempt fired the short case stretched resulting in a case separation?

    Is it possible to push a shoulder back that far resulting in enough stretch to separate the case?

    Thanks
     
  13. WiskyT

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    Yes, that's possible. It's not particularly likely though. Also, when a case fails due to excessive headspace, they usually (always?) fail all the way around just above the extractor groove. It looks like someone sawed the case head off.

    [​IMG]
     
  14. steve4102

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    OK Thanks.
     
  15. steve4102

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    Note the position of the case fully chambered in a Mini-14.
    http://charlie6.org/c6forum/download/file.php?id=345&t=1

    The unsupported area coincides with the expanded portion of the case in picture #1. To me this indicates that the bolt was locked up and this was not an Out-Of-Battery Fire?

    What do ya think?
     
    #15 steve4102, Sep 28, 2011
    Last edited: Sep 28, 2011
  16. fredj338

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    If that is true & the gun is not defective, then you may have excessive headspace in that rifle. The mini is not known for tight tolerances & since you must FL resize for best results, you could be getting excessive stretch & eventual head sep. IMO< an over pressure round would not have give a head sep unless it was waaaay over pressure. You should see enlarged primer pockets (loose primers) first, maybe rim damage from extraction as well. It's diff to read pressure signs in semiautos, but a head sep is not a common event. Your pic though looks like an OOB firing, not a headspace issue. Ruger may be telling you their rifle won't fire OOB. I think Glock claims the same thing & everyone knows the GLock will fire OOB.
     
    #16 fredj338, Sep 28, 2011
    Last edited: Sep 28, 2011