Re: colt revolvers in 455
There is an interesting thing about the SAA made for .455 and .476. The .45 Colt was made with a very small rim so it would fit into a cylinder that was made on the same tooling and only a bit larger than the .44 New Model Army cylinder. But the .455/.476 has a normal size rim (.530" vs .505" for the .45 Colt). How did Colt do that?
First, they enlarged the frame window to take a slightly (.021") larger cylinder. Then they bored the chambers at a slant (convergent), so the rounds sit a little skewed in the cylinder. Reportedly, the firing pin hits off center, but the guns work OK.