Thread: Which calibre for a Martini Henry project?

Bear in mind that the Matini-Henry action needs to have the firing pin diameter and protrusion reduced and a hardened steel firing pin bush fitted into the face of the breech block before they are safe to use with high-pressure modern cartridges (eg. in excess of 40,000 psi) or the cartridge pressure can force the large diameter firing pin backwards when fired. This results in a ruptured primer, severe gas erosion of the breech face, and hot gases in the face of the shooter. The .303 Martini-Enfield actions usually have had this modification done in the 1890's when converted at Enfield. Personally, I believe that your best ruults will be with the .45/70 and leave the hotter cartridges to more modern actions.