The rifle was engraved by Purdey's best engraver, James Lucas, barrels by the head barrel maker G. Austin, hardening by Abbe Robins, stocking by Henry Lewis. Purdey records list the rifle as a 28 BORE. The bullets mike .575 and weigh 455 grains. The rifle has a tapered bore and mikes as best as I can tell .557 at the muzzle.