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Thread: case head separation? Murphy?

  1. #1

    Question case head separation? Murphy?

    What would cause case head separation on a 300 win mag.

    A sign of excess headspace?

    Reloaded to many times with weak brass?

    Murphy your expertise would be appreciated.

    thanks

  2. #2

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    The case too far forward in the chamber when the powder ignites, the increase of pressure will press the shoulder and body walls hard against the chamber walls, but the head will be pushed back far enough to separate the brass at the thinnest point not grabbing the chamber wall.

    right???

  3. #3
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    Although I am not Murphy perhaps I can offer an opinion. First thing I would do is stop full length resizing your brass. Next time you resize a case start with neck sizing only and then try screwing down your resizing die 1/8 of a turn at a time and resizing till you are at the point the bolt will close on the case with just a tiny bit of resistence.
    Try this with new brass and see what happens.
    I am assumming the headspace on your chamber is correct and has been checked?
    Tennessee

  4. #4
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    Bernie,

    Your title makes it look like my head has separated, which of course is likely.

    I need more details but will make some assumptions in the mean time.

    Belted mags head space on the belt.

    Full length sizing pushes the shoulder back...some.

    If your chamber allows the shoulder to move forward when fired (that's very common), this will separate the case just in front of the belt in only a few firings. The case stretches and will show a ring ahead of the belt. This ring is a thinner ring of brass where it stretches at each firing. It will stretch at the first firing but not again if you allow the case to "head space" on the shoulder. (That's really not the correct term since the belted cases headspace dimension is from the case head to the front edge of the belt.) If we only neck size or more correctly partially full length size the case and donot push the shoulder back from the position it was left in after firing, case stretch will be minimum.

    Now each rifle is different. My son-in-law has a 308 Norma that will separate on the second or third firing if it is full length sized. Chambers have space between the factory ammo (or new brass) shoulder and the shoulder of the chamber. The case will grow to fit on the first firing. Don't change that shoulder position.

    Let me know about the details of the case failure. Where specifically is the separation.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  5. #5

    Question

    Right after the belt on the 300 win mag case.


    Could this be a sign of excess pressure? I always thought signs of pressure were, bright rings around the base, primers flattened, soot from around the primers, and or cases hard to extract.

  6. #6

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    almost sure it was a once fired brass. neck resized.

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    Quote Originally Posted by Bernie1 View Post
    The case too far forward in the chamber when the powder ignites, the increase of pressure will press the shoulder and body walls hard against the chamber walls, but the head will be pushed back far enough to separate the brass at the thinnest point not grabbing the chamber wall.

    right???
    Ahhh! No.

    The case is held against the chamber at the belt, not at the shoulder. You have to correct that when you reload the case. Adjust the dies as Randy said, donot push the shoulder back. Your rifle may have a little more "space" at the shoulder than some rifles but the critical dimension is case head to belt, and I'm sure that's fine.

    Actually the case is held at the back and the rest of the case moves forward under pressure at firing, and stretches at the rear most part of the body. Just ahead of the belt.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Get a scribe and with it you can feel from the inside of a case any case that may have a seperation about to happen upon the next time it is fired.

  9. #9
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    Like Allen suggested......but for a scribe get a paperclip and bend it into position so you can insert it inside the case and "feel" along the bottom of the case to see if it is beginning to stretch.
    Tennessee

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