Manufactures have to stay with a length that will fit any chamber and magazine for any gun to feed proper. Being a single shot and if the ammo isn't going to be used in a magizine that feeds a rifle you can make the COL any length you want as long as it works in the gun intended.
Unless the barrel is a custom it will probably be cahmbered to fit any of the larger bullets so my be long throated when using light bullets.
