9.3x57
(.450 member)
27/08/07 06:47 AM
Re: Proof loads

Quote:

For example, the .470 Nitro Express has a CIP standardized MAP of 39,160 PSI. That means that, by law, the cartridges used to prove a new .470 Merkel, Heym, Krieghoff, Purdey, etc., produce 48,950 PSI. When do pressure signs start on modern drawn brass cartridge cases, and modern stainless boxer primer cups? Engineers at manufacturers like Hornady usually say around 62,000 PSI. By the time conventional pressure signs begin to appear on handloads, you're WAY past PROOF. Pressure signs simply can't be safely used as a guide when handloading for doubles.




Excellent point and well said.

This very same point has been made in the past about the working up of loads for various lever guns. For example, the guy satisfied with loads backed off just a bit to eliminate flat and cratered primers in an old Marlin 36 or Winchester 94 may even so be straining the action. I think your point needs to be heeded by anybody loading for any break action, lever, pump {like the Rem 14, etc} or other oldie like a Snyder or Trapdoor Springfield.



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