50-70 wouldn't work in mine without some modification. Turn the rim down & shorten them up a bit. Bore size will vary as well between different guns. I've measured them from .509 up to .515.
I have seen 12.17x44R brass turned from solid rod at the Cal gun show..very thick walled compared to extruded brass, would probably work tho with a shouldered bullet similar in design to what a .41 LC uses.