The other thing that it will do, is once the preservatives are eaten up, is go after the burn rate conditioners which changes the burn rate of the powder. Nitric acid is will etch the inside of a brass case and even eat all the way through it over time. The purpose of the preservatives is to be “sacrificed” as the nitrocellulose breaks down over time, and one of the byproducts of this breakdown is nitric acid. Single base smokeless powder is a mixture of nitrocellulose, binders, preservatives, and burn rate conditioners. So, with that data in mind, lets ask ourselves why all the older ammo had a much higher max average pressure then new commercial ammo, despite having essentially the same external ballistics? The answer lies in the chemistry of smokeless powder. The Rem-UMC headstamp was discontinued around 1959 and transitioned to the R-P headstamp for “Remington Peters” so whatever ammunition Larry shot, it was at least 57 years old based on possible latest date that Remington could have made that particular headstamp on 7×57. All of the new manufactured commercial ammunition in his data set are below 51k PSI except for the Rem-UMC 175 RNFMJ load, which is pretty dang old. This data, combined with pressure data for surplus and commercial 308 Win and 7.62×51, convinced Larry that the Small Ring Mauser’s are essentially safe to shoot with 7.62×51 ammunition, because so many of the 7×57 loads tested were above the 51k PSI SAAMI max. You can see Larry’s original post here: ×57-psi-for-use-in-sr-mausers/ Larry and I have been arguing about the relative safety of small ring Mausers for fifteen years now, and I’ve come to the conclusion that “He may be right, but I’m not wrong.”
Someone I respect, Larry Gibson, has used his ballistics lab to produce some data. For years debate has gone on about exactly what is the “safe” pressure levels for small ring Mauser actions.
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