I don't know about Fiocchi ammo, but if I were going to try another case in my converted .455, I might look at .45 Auto Rim, assuming that the case rime will fit as well as .45 Colt. But, I also assume that would cause the same kind of cyminder ring problem shooting .38's in a .357 Magnum or .44 Specials in a .44 Magnum would create. For the time being I'm sticking with .45 Colt.