I don't think apple really likes guns, so it would probably have to be third party, but a training pistol with a real belt-mounted holster and an AR upper and lower without the FCG or barrel, both with some tracking markers the Apple goggles can pick up would probably work well. Shooting a rifle with VR controllers does not really work that well, because you can't brace them at all (because the two standard controllers are not attached) and there is no stock. Fix that with a hundred dollars of airsoft knockoff AR-15 parts.