I have an Alexander Henry in the more “common” 450-400 2 3/8”. It is a very mild shooting cartridge. I was able to find dies from Hornady, and for brass, I sacrificed some of my beloved .450NE brass, cut them down with a pipe cutter, sized them in the dies and trimmed to length. For bullets, I’m using cast .411” lead using a mold intended for a .41 magnum pistol bullet. I do use a NFB load of smokeless and backer rod foam filler. Graeme Wright’s book, “Shooting the British Double Rifle” has a tiny entry in the appendix from which I based my powder selection and charge weight on. My rifle has Damascus barrels and have thus far not had any issues with unintended Ka-booms......