I own an old Birmingham, Clabrough and Johnstone, sidelock double gun, 12 gauge, 2 " chambers, proofed under the 1904-1925 rules. My question, does anyone know what pressure these old Birmingham guns were tested to. I understand that later on (1954) they were proof marked 3 tons per square inch, does that mean 6500 psi? I am trying to figure out what is safe to shoot through it. I had been using the Winchester AA, Low Noise Low Recoil Target loads but have recently found that Winchester rates these loads at 11,500 psi? Winchester Ammunition
Thanks.
Tim