The large case was meant to be filled with blackpowder.
A good load is 35gr Goex FFFG and a 250gr bullet.
The results, as published by Mike Venturino in his book, "Shooting Single Action Revolvers", show a 35gr GOEX/250 gr load to produce 970 ft/sec from a 7-1/2" Colt's SAA.
As far as guns, I recommend SA revolvers for the .45 Colt chambering.