My old friend Millsman will forgive my gently pointing out that Forsyth's original patent was not for a percussion cap, per se, but for a lock (roller primer or "scent bottle", sic) which used a small magazine of a priming powder for igniting each shot. And there are a number of claimants for the invention of the percussion cap including, according to George, Colonel Hawker/Joe Manton, James Purdey and Joseph Egg. This was a time of pellets, powders, tubes and paper patches, et al, and the idea of a pellet being inserted into a closed end tube to produce a "cap" seems to have occurred to a number of people around the same time. Steel, pewter and copper were all employed - even, of all things, an old umbrella ferrule - but there can be no doubt but that Joshua Shaw's idea came out in 1814 using a reloadable cap made of steel, followed in 1815 by an improved cap made of pewter that could be thrown away after use, followed again in 1816 by a cap made from sheet copper that we would recognise today. This work seems to have been carried out in England, but Shaw, a landscape painter, lived in the US in the latter part of his life.
Shaw is therefore usually credited with the invention, and I agree that the US would have known of it from a very early stage.
Alan1
Shaw is therefore usually credited with the invention, and I agree that the US would have known of it from a very early stage.
Alan1