Oversize flash hole/case rupture

Discussion in 'Reloading Forum (All Calibers)' started by Dave Marshall, Jan 17, 2019.

  1. Dave Marshall

    Dave Marshall

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    Posing a question for the brain trust here.

    What is the likely effect on internal pressure of an oversized flash hole in a centerfire rifle cartridge?
     
  2. john pruitt

    john pruitt

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    not enough to worry about that is for sure
     
  3. Dave Marshall

    Dave Marshall

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    I had a catastrophic case failure. Trying to figure out why.
     
  4. Bc'z

    Bc'z Gold $$ Contributor

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    Explain please
     
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  5. Dave Marshall

    Dave Marshall

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    I had a brand new 6xc case fail where the rim meets the body. It ruptured completely and did some damage to the rifle and shooter. This is also the only unsupported area of the chamber. I was able to find most of the debris and all of the ruptured case. The flash hole is considerably oversized and oblong in shape. So far, the flash hole is the only thing I can see that is not normal.
     
  6. Bc'z

    Bc'z Gold $$ Contributor

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    Thanks.
    Winchester brass?
     
  7. Dave Marshall

    Dave Marshall

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    No, Winchester doesn't make 6xc brass. There are only 3 manufacturers of 6xc, and I'm not going to trash any of them here.
     
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  8. rwj

    rwj Silver $$ Contributor

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    I hope that you were not seriously injured and have fully recovered!

    You stated that the case was new, is the same true for the rifle?
     
  9. 243winxb

    243winxb

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    https://apps.dtic.mil/docs/citations/ADA606635

    Primer pocket with enlarged (flash) spit-hole (0.110 in diameter), tested.

    The military test shows less pressure with the larger flash hole, if i read it correctly?.

    Some brass is formed using 2 units. The case head is stamped. The body starts as a tube. They are pressed together under high pressure to form a unit. Then formed.

    Some brass may fail.
     
  10. Dave Marshall

    Dave Marshall

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    I was incredibly lucky. I have a bad habit of shooting without glasses. It's obviously not wise. The case ruptured and vented gases out the magazine well and along both sides of the bolt. The magazine was blown out and the bottom metal deformed. The extractor (sako style) was blown off and hit my cheek. The bolt catch was also blown off. I was hit with shrapnel on my cheek and just above my right eye. My eye was amazingly unharmed. INCREDIBLY lucky. It's a huge lesson for me and I hope others as well.

    The rifle is not new. I had an older barrel with a smaller chamber re-chambered with a larger reamer. I fired one round with no issue and the following round blew up the rifle. I have fired over 100 pieces of the same brass without issue. The first fired case measures as expected. There were no obvious issues with chamber dimensions in the fired case.
     
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  11. Dave Marshall

    Dave Marshall

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    Thanks for posting that report. I had only seen a report of testing with smaller flash holes.

    This largely answers the questions.
     
  12. Mulligan

    Mulligan Gold $$ Contributor

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    Wow!
    Thanks for sharing.
    Please keep us posted
    CW
     
  13. 243winxb

    243winxb

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    I dont see a SAAMI standard. The 6xc is still a wildcat? Tubb desigh? Interesting.

    http://www.6mmbr.com/6XC.html
     
  14. Rsadams

    Rsadams

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    Carbon ring..?
     
  15. Texas10

    Texas10 Gold $$ Contributor

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    Any possibility that the case was trimmed too long for the chamber, resulting in a pinched bullet? I have seen the same thing happen in the same sequence before. First round shoots normally, next round Ka-Booms. Brass head expanded out, primer blown out, bolt disassembled violently. In checking other loaded rounds in the shooters box many were found .02 and more over max length, and that particular shooter did not own case trimming tools, just chamfering tools.

    Not saying you'd commit any of these sins, just exploring possibilities.
     
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  16. GotRDid

    GotRDid

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    “Some brass is formed using 2 units. The case head is stamped. The body starts as a tube. They are pressed together under high pressure to form a unit. Then formed. “

    Where can we find further info/video of such a process?
    GotRDid.
     
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  17. 243winxb

    243winxb

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    google patents search http://www.google.com/patents/EP2552619B1?cl=en Not saying this is/was the problem.

    Brass - drawing vs extrusion. The extrusion of brass may not be the SAFEST METHOD of making brass. The cartridge case is manufactured according to the method of the invention as defined in the claim from a conventional seamed or seamless pipe, from which the final shape of a tubular section B is formed with cold forming of the pipe. Then a bottom C of the case, which had been produced by cutting, is joined with the formed pipe section B in various ways like welding, soldering, forming, pressing, etc. in order to manufacture a cartridge case. Figure 5 cartridge case in cross-section manufactured according to the method of the invention before and after placement of the bottom C of the case to the deformed pipe B. New patent 2010.
     

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    Last edited: Jan 17, 2019
  18. Dave Marshall

    Dave Marshall

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    Kicking the possibility around. If there was a ring, and the chamber was cut a couple thousandths deeper, it could constrict the case mouth in the ring.
     
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  19. Dave Marshall

    Dave Marshall

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    It is possible in a way. The cases are new, and the correct length. The neck of the chamber may be artificially short due to carbon build up. The effect would be similar to having cases that are too long.

    Gunsmith will be getting a borescope in there soon. I may have him cut the barrel lengthwise for a good look too.
     
  20. Texas10

    Texas10 Gold $$ Contributor

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    Or maybe make a cast of the chamber?
     
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