Oyeboteb, that Cowboy Action Shooting round your thinking of is the 45 Cowboy Special made by a cowboy by the name of Adirondack Jack. The dimensions are those of a .45Colt shortened to 45acp length. It has the case capacity of a 45acp and uses the same loading data. It was intended to solve ignition problems that happen when you put a little bit of powder in that huge 45Colt case; which it does superbly. I think Jack has Starline make the brass and it stands up well to reloading. How do its dimensions compare to the .455 cartridge ?