Proof Markings
Prior to the barrel being mated with the action it needed proofing to ensure its stability, at Enfield, barrels were proof tested in the RSAF’s own proof house, in Birmingham at the Birmingham Proof House.
1P (First Proof) To achieve “First proof”, the barrels were aligned in a “battery” of up to 20 barrels side by side in proof tank, the breech end of the barrel having been threaded and a cap with a touch hole screwed onto it. Into the barrel a 715 grain proofing bullet was rammed over a large 205 grain charge of gunpowder in a muzzle loading style. The battery was then exploded simultaneously via a pull on a lanyard, which in turn released a hammer. After firing the plug was removed, the barrel washed and inspected for bulging or failure, after passing this process the barrel was then marked with an inspection mark (1P)
2P (second Proof) Once the proofed barrel was inspected the barrel would be passed for thread cutting and chamber reaming to suit the cartridge, during each process the worker would inspect each component with a variety of special gauges, on his satisfaction, further inspection marks were added during each view under the barrel. The barrel was then mated to the action body, known as “breeching”. The barrel was dated, and then offered for second proof. Second proof consisted the firing of a purpose made “Proof round”, a boxer cartridge containing a 715 grain lead bullet over 137 grains of powder to again test its integrity with a hugely over powerful charge. On passing this test both the barrel and action were viewed and was marked 2P for second proof
