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Thread: 45/70 Case Bulge

  1. #1

    Default 45/70 Case Bulge

    Load is as follows:

    Cast Performance 405gr WFNGC
    New Winchester brass trimmed to length
    47gr H4198 (1gr above min according to Cast Performance)
    Fed 210
    OAL 2.550"
    Heavy crimp
    Fired out of a Marlin GG

    Where the head case meets the body is a bulge on every peice of fired brass (12 so far). It's not a consistant bulge around the case but more so half of the diameter which measures out to .510", new brass measures .500". Is it typical to see a bulge in the brass with a stout 45/70 load out of a GG? Can anyone explain this to me?

    The left peice is new unfired brass and the right is a fired piece with the load above.


  2. #2
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    Yeah, I think so, with a Lever Action.

    My 30-30 cases look that way, if they've ever been fired.

    Isn't that the solid part of the case there, that don't expand?

    Smitty of the North
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  3. #3

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    That ctg chamber is large to allow for dirt in the old days and the brass will expand to fill the space. It is uneven because the pressure is not great enough to give a true fireform. I have always lapped my dies so I did not resize that area and work the brass till it becomes brittle. Just neck size and have fun they will just expand to fill the chamber. I don't recall the loads I used but they filled the chamber in the first shot. I don't know why the makers don't use a reamer matched more to the case size..

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    When Mathew Quigley made his reloads for his 3 1/4" Sharps 45 rifle, there was likely no bulge in his cases and he only neck sized his case when he wasn't using his paper patched bullets. With paper patch, no sizing was needed so field loads were quick and easy. Don't ya love it when a gun guy makes a movie.

    The old 45-70 with todays cases and yesterdays loads does not operate at pressure levels that will bulge brass regardless of how sloppy the chamber size. Your load is not a trapdoor load and reaches enough pressure to expand the cases slightly. That case looks very normal to me and will likely be reshaped with you f/l sizer. The bulge in any case never seems to be symetrical or go full circle as we would expect, but it is a very normal sign of operating pressure results. As Smitty said the solid web of the case doesn't expand and you can see how far the web goes on those strong cases. (Actually Ken Waters measured this web expansion and tried to correlate it to pressures) And as has been mentioned, the case will conform to the shape of the chamber when pressure is enough. Many loads we shoot in the 45-70 do not reach the level to expand the brass, or not enough to expand it out enough so it doesn't spring back. I think that is about 30,000 psi when we start to see this. You're well into safe territory for any Marlin, but beyond what a trapdoor would take. I use RL-7, about the same burn rate as 4198 and stop at about 50 grains with 400 hard cast in the Marlin. Nice pic BTW.
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  5. #5
    Member jdb3's Avatar
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    Only one problem Murphy, Quigley uses a 45 7/8 better known today as the 45-110. Jim

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    Quote Originally Posted by jdb3 View Post
    Only one problem Murphy, Quigley uses a 45 7/8 better known today as the 45-110. Jim
    You're right. A 2 7/8" case and it is only a 110 when paper patched. If you seat a lubed 540 grainer into the case it won't hold 110 grains of any size. Thanks for officiating my blunder.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  7. #7

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    Once again, thanks guys for the help. Once I ran a fired brass through the FL sizer the bulge was almost non existant. To date I've used only new brass in my GG.

    On a side note, I have always FL size my fired brass. I have heard hunting horror stories of rounds not chambering when on game due to brass that was only neck sized. Atleast, those were the suspected causes. I've always thought about trying neck sizing instead of the FL sizing but havn't given it a whirl yet. Is there any possible truth to this possible myth?

    Thanks Murph, it took me awhile to get the pic satisfatory. I hate it when someone asks for advice and post a picture that looks like it was taken through beer goggles.

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    Moderator hunt_ak's Avatar
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    Grem, we were shooting Alaska_Lanches GG and I noticed the bulge as well....just FYI

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