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  • StickShaker

    Active Member
    Mar 3, 2016
    888
    Montgomery
    I happened to catch this on a 9mm. No evidence of it on outside of the case and I'm guessing it's a manufacturing defect. Just tried to pry the edges up with an x-acto knife but it won't budge. I'm curious to see how deep it goes so I'll grind at it with a Dremel tomorrow.


    P8250007.jpg
     

    noylj

    Active Member
    Jun 3, 2012
    144
    Molten brass hitting the web of the case?
    Now, take a picture of a sectioned .40 S&W case and see the difference in web thickness/length.
     

    StickShaker

    Active Member
    Mar 3, 2016
    888
    Montgomery
    Molten brass hitting the web of the case?
    Now, take a picture of a sectioned .40 S&W case and see the difference in web thickness/length.

    Cases are formed by cold drawing a slug of brass. It's hard to see because of the darkness but the crack doesn't extend into the base much farther then shown. I initially thought it was a thin flap that could easily be peeled up but that wasn't it.

    .40 S&W thicker or thinner?
     

    noylj

    Active Member
    Jun 3, 2012
    144
    Just wondering if some piece of brass somehow got melted and flowed there (we KNOW the case is cold formed). Would have NO idea how it could happen, but what you show is hard to understand either...
    When I looked at a .40 S&W case, I was shocked at how thin and short the web was compared to a 9x19 case for having to withstand the same pressure. After having a .40 case failure (first and only case failure in over 40 years), I am rather spooked by .40...
     

    Blacksmith101

    Grumpy Old Man
    Jun 22, 2012
    22,154
    That was probably a lap formed when the sheet of brass the blanks were punched out of was originally rolled at the mill. Used to see things like that on a larger scale in steel plates used in shipbuilding. Manufacturing processes and quality control have gotten so good that rolling mill defects are seldom seen by the final consumer. If that had been on the outside it would have been rejected before the case was ever finished the drawing process.
     

    StickShaker

    Active Member
    Mar 3, 2016
    888
    Montgomery
    That was probably a lap formed when the sheet of brass the blanks were punched out of was originally rolled at the mill. Used to see things like that on a larger scale in steel plates used in shipbuilding. Manufacturing processes and quality control have gotten so good that rolling mill defects are seldom seen by the final consumer. If that had been on the outside it would have been rejected before the case was ever finished the drawing process.

    That sounds like a good explanation, thanks!
     

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