The 45 Colt was the original caliber of the 1873 Colt. I've always shot 45 Colt in my single actions, that's all I buy for me. I have nine or ten of them now, I forget. I also use an 1866 in 45 Colt. Besides that, its real easy to load, doesn't need to be lubed, etc, and will knock down anything with the right load. The only concession I've made for SASS matches is to download my shells a bit so I wont scare my fellow posse members.