Found one of the references I was looking for so maybe this will help resolve the pressure issue - at least for 16ga: "Story Of European Proof Marks" by Englehardt Part II, Chapter II Proof In France.
St. Etienne Proof Loads between 1885 and 1923 (Chart inserted in the text) shows the Proof of finished barrel produced 893 Kg/sq CM. The extra strong proof was 1050 Kg/sq CM, Double Proof was 1472 Kg/sq CM, and the Triple was 1800 Kg/sq CM. The same chart also shows the normal load of 16ga shotgun cartridge in France during that time was 438 Kg/sq CM. There is always discussion about the absurdity of the pressures in the double and triple proofs, but in pursuing a realistic answer to the original question the 438 Kg/sq CM service loads might give us a reasonable response of approx 6230 psi. There will be problems in the conversion as we don't know exactly how these pressures were measured but quite probably by LUP so we can add about a 1800 psi to that for stress gage pressure reading equivalents as I recall. So an old 16ga prior to 1924 was probably intended to handle around 8000 psi as measured by strain gage. This seems consistent with other things I have read. Guess if I were reloading for such a gun I might choose to stay more toward the lower numbers around 6500 psi out of respect for age. However I routinely shoot CIP 2 1/2 inch 16ga shells in my gun from that period without trouble with pressures around the 8000psi end of the scale though.
If there is better guidance on my meager conversion knowledge please chime in.
Last edited by Jerry V Lape; 12/30/06 08:58 PM.
