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Thread: Reformed Brass in relation to Maximum Recommended Chamber Pressure

  1. #1

    Reformed Brass in relation to Maximum Recommended Chamber Pressure

    Hey fellas. Ive looked through a few pages of backlogged threads and didn't find what I was looking for. I've been reforming LC 1969 .30-06 brass into 7x57mm for a little bit now. I bought a 5 gallon bucket of .30-06 brass for a few bucks because I can use that to form 7.7 Jap, 7.92x57mm, 7x57mm, and 7.62x51. I sorted about 80 cases by headstamp specifically for my Brazilian Mauser. Ive been working on loads using 175gr bullets, 168gr bullets, and probably today, 139gr bullets. Im interested in recreating military spec ammo so the rifles sights are properly calibrated for the ammo I make. Ive been looking for a 7x57mm load using CFE 223 because Im sitting on an 8lb jug of it. Ive found 7mm-08 load data using CFE 223 but nothing for 7x57mm. While 7x57mm and 7mm-08 have almost identical ballistics, they operate at different pressures. Around 60k psi and 56k psi respectively.

    This is my question: if a case with a lower advertised MAP is formed from a case with a higher MAP (forming 7x57mm out of .30-06), will the ACTUAL max average pressure of the newly reformed case be higher than a factory produces case of the same type, or what? Would you be able to bump up the pressure a little bit in a 7x57 formed from a .30-06 compared to a factory 7x57mm?

  2. #2
    Boolit Master
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    No, or maybe a very little.

    But since you don’t have a way to measure pressure I don’t think messing around at or above max pressure makes sense. That said, for my purposes 56k and 60k psi are functionally equivalent.

    Edit: flame proof suit on

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    Boolit Master Good Cheer's Avatar
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    Have you found a need to turn the necks?

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    Quote Originally Posted by Good Cheer View Post
    Have you found a need to turn the necks?
    No, actually. And im glad too. Neck turning seems like a rel pain.

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    Boolit Grand Master Harter66's Avatar
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    Have you ever weigh lotted brass ?
    I did a bunch of LC once cases ran from 179-207 gr . 20gr of brass is a lot of case space .

    Now if you find your getting higher than advertised velocities I'd say your cases are smaller volume and pressures are higher .

    Check water volume against known cases then you'll know 100% what the capacity is of your cases .

    The case volume can vary from lot to lot , line to line , and brand to brand by at least as much as any of each or another.
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  6. #6
    Boolit Master
    dtknowles's Avatar
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    I believe that 7mm Mauser pressures are kept lower becuase of some weaker actions chambered for that round. I don't know what action is used on your gun but it could be higher pressures would be acceptable. No telling with substituting loading data from one caliber to another, you are kind of on your own.

    Tim
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  7. #7
    Quote Originally Posted by dtknowles View Post
    I believe that 7mm Mauser pressures are kept lower becuase of some weaker actions chambered for that round. I don't know what action is used on your gun but it could be higher pressures would be acceptable. No telling with substituting loading data from one caliber to another, you are kind of on your own.

    Tim
    The "Brazilian" Mauser Mod. 1908 is an iteration of the Gew. 98 action. Im not really worried about damaging the action. However the MAP numbers I've quoted for the 7x57mm are from the CIP, not SAAMI. SAAMI states the max average pressure is 51k psi in in "deference" to 1893 Mauser actions and ratted out 100 year old surplus. The CIP states the MAP for 7x57mm is 56k psi. Apparently the Europeans are willing to allow old rifles to stretch their legs. (Take a look at US produced 8mm Mauser. Some of those loads have the energy of a .30-30 instead of a .30-06, compared to European produced 8x57mm.)

    That being said, the MAP of the .30-06 is 60k psi according to SAAMI. And most of that pressure is held by the case head and web. If that case is then mushed into the shape of a 7x57mm case, would it still be able to contain 60k psi? If not, what changes?

  8. #8
    Boolit Buddy
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    Quote Originally Posted by TerkyJerky View Post
    That being said, the MAP of the .30-06 is 60k psi according to SAAMI. And most of that pressure is held by the case head and web. If that case is then mushed into the shape of a 7x57mm case, would it still be able to contain 60k psi? If not, what changes?
    The strength/elasticity of the metal surrounding the case?

    45_Colt

    edit: and the strength/elasticity of the locking lugs of the receiver/bolt

  9. #9
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    Wayne Smith's Avatar
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    Since you have a 98 Mauser action I would not worry about the cases. They are as strong if not stronger than the original - since they are all based off the same case anyway. Your other actions I cannot speak to, but your 7 Mauser should hold the military round equivalent without any problem. I would not try to make it a 7mm Mag, though.

    It might help you to read through some of the old research done by Col. Askins and others after the war. Destruction testing showed that he could cut the chamber of a rifle down to several thousands of an inch before it let go when fired - i.e. burst the chamber. Primary issue is force against the bolt, and again, you have a strong action.
    Last edited by Wayne Smith; 12-02-2022 at 04:03 PM.
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  10. #10
    That's what I suspected. The surplus actions I have are Mausers, Lee Enfields, Arisakas, and a Mosin. I have no interest in hotrodding any of these, but I want full power military spec ammo. And sometimes load data watered down by lawyers can barely reach proper velocity before the chamber pressure "maxes out"

  11. #11
    Boolit Grand Master Harter66's Avatar
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    Measure the brass and it's capacity.......

    I just formed some 6.5CM for 6.550SR Japanese. Some guys about 80 yr ago ran an 06' reamer in a type 38 6.5 and dropped an M2 ball in it and fired it . It stripped the barrel threads off leaving them in that action . The CM is rated at 61kpsi and the Japanese is only at 51 kpsi , but I won't hurt the action with proof loads all day so I should be ok to load CM data right ? I mean it's a no trim conversion and the groove is .270 instead of .264 and throat erosion and the shallow Metford rifling so I can't possibly hurt anything. Right?

    I might use CM data in a 260 Rem and 260 Rem in a 6.555 but I'm not using 6.5-06' data in a 6.555 even if it's an AI . The same applies to every other cartridge I load .

    Shoot whatever data is available but some powders get weird in case volumes with some bullet dias . H322 works well in 223 , 6.8 , and 45-70 but you don't see it in 308/Mauser/06' family cases . 4350 you can max out just barely, 4831 passes that point with up to 175 gr bullets in 757 .

    Case capacity makes all of the above wrong or at least not accurate.
    In the time of darkest defeat,our victory may be nearest. Wm. McKinley.

    I was young and stupid then I'm older now. Me 1992 .

    Richard Lee Hart 6/29/39-7/25/18


    Without trial we cannot learn and grow . It is through our stuggles that we become stronger .
    Brother I'm going to be Pythagerus , DiVinci , and Atlas all rolled into one soon .

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
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GC Gas Check