Was the bore actually tapered, or 0nly the bore tapered, or was the rifle of progressive depth rifling. There is a distinct difference as with a tapered bore, the grooves would also have be tapered in depth for the tapered bore to be effective, or the rifling would be shallow at the breech, and deeper at the muzzle, where it was proved in the 1850's and 60's that the reverse worked perfectly.

The Enfield Minnie Rifles of the 1850's, the 3-band, 2 band rifle and 2 band Musketoon were cut with progressive depth rifling, which swept Europe and the USA in the 1850's. All of the USA and French guns as well I think, had progressive depth rifling, that is, the guns meant for the hollow based "Minnie Ball". With this rifling, the depth was .008" deeper at the breech than at the muzzle, thus with .003" depth at the muzzle, and a .577" bore, they had a .583" groove diameter at the muzzle, but .599" groove diameter at the breech, still with the .577" bore. It did not matter if the barrel was 24", 32" or 39" - the depths remained the same. The USA Minnie Rifles were thus rifled as well, including the .69 Muskets that were returned to the armories and rifled for the 730gr. Minnie Ball.