dad divided up the heirloom firearms about 8 years ago and my brother got a "73 Winchester" and it is marked as 38-70 caliber. I once saw a single round of ammo for this very rifle that one of the distant cousins had. Not planning to shoot the gun but be nice to have a box or so of ammo just to know what they were like. As I remember they were very slightly shouldered but mostly tapered. Any information on where I might get some brass or loaded ammo for this gun or information on the cartridge and how long and when Winchester used it?? Thanks, 10 ga