i have 2 enfield 2As that were converted to .410 musket in 1930 and 1931 for use by the indian army. that is a 303 brit fireformed to 410 bore and resized with a 41 mag sizing die. ill dig up the load i used, it was a pistol powder with cream of wheat for the load and held straight up and fired. you loose some to splits the first time and they trail off afterward