Most countries which had proof laws required both a Provisional Proof & a Definitive Proof. Provisional proof was done to the rough bored tube using a breech plug as stated & loaded from the muzzle. The definitive proof was done to the assembled gun, normally in the white, so used a shell casing. This load was normally a bit lighter than the provisional load, but still beyond the capacity to fit a standard hull. At some point, I forget the exact date, England did make provisions, at the makers discretion,Several of the companies indicated they used the British proofs in their guns. of proofing only by the definitive proof & foregoing the provisional but in this case the gun would be proofed with the full provisional load. I have one Birmingham proofed gun which shows this special definitive mark & no provisional mark.
I still have some info which was sent to me back in 2005 by Greg Taggart, taken from the May/june issue of Army Ordnance. This was presented by Calvin Goddard & pertained to Proof Practises of manufacturers in the US. From British Rules & regulations of 1925 for the 2 3/4" 12 ga the proof load was 7˝ drams of black powder FFFG) with 2 oz of #7 drop shot. It was noted the shot was to be contained in a rolled paper capsule with felt wads at each end (specified sizes given) & held in place in the cartridge by glue or shellac. Mean pressure to be developed by this load was 15,900lps/7.1 tons with a minimum individual of 15,200lbs/6.8 tons & a maximum individual of 17,500 lbs/7.8tons
This practise seems to have been followed at this point in time by Hunter Arms, Iver Johnson, Parker Bros, Remington Arms, J Stevens & Winchester Arms. Ithaca stated their guns were proofed with a double charge of powder & 1˝ time the normal shot load to produce a proof pressure of approximately a 40% increase over a normal load for the gun.
