I once saw a 45/70 rifle that took a cartridge but the primer was external to the cartridge. The primer pocket had a flash-hold in it which the primer flash pass through and ignited the main charge inside the cartridge. You preloaded a 45/70 case. Technically it was not an M/L. May have had a place at Friendship but hardly at a Rendezvous. ......
Be Safe !!!