The 500 Bushwacker can only be built on the BFR Long Cylinder frame and it is easy to do on a 500 S&W long cylinder BFR. But TII Armory can make any BFR long cylinder model into the 500 Bushwacker. The muzzle brake they attach to the barrel is mandatory. They say it cannot be shot safely without the muzzle brake. The Double action X-frame revolver from S&W cannot be made to work with the 500 Bushwacker cartridge.