RE: .45 ACP and .45 Auto same thing?
As others have said, 45 auto and 45 acp are in fact the same, but for some that dont know " just for some info" there is also a 45 auto rim cartridge which cant be fired in a 45acp pistol, made for the model 1917 revolver produced by Colt and Smith&Wesson durring WW I. It has a full rim to be used with half moon clips for ease of loading and unloading, the revolver can fire the 45acp round in it though without the half moon clips. Just a tid-bit of info!.