Q. Can you safely shoot a .45 Auto Rim cartridge in a revolver chambered for a .45 Colt? A buddy of mine gave me some the cartridges, but I don’t have a gun in .45 Auto Rim. I do have a .45 Colt, though, and it looks like it should work.
A. I would not encourage anyone to attempt to fire a .45 Auto Rim cartridge in a cylinder chambered for .45 Colt. Aside from differences in the dimensions of the cartridge case, the Auto Rim round has a significantly thicker rim, approximately 0.090" versus approximately 0.060". This could certainly cause headspace and functioning problems. If the revolver in question is supplied with a separate cylinder specifically for the Auto Rim cartridge, there should be no problem. A number of firearm manufacturers have over the years offered .45 revolvers with dual cylinders, one for .45 Auto Rim or .45 ACP cartridges and one for .45 Colt.