The factory 460 S&W muzzle brake is for jacketed bullets only. The muzzle brake for use with cast bullets only seals off the top ports of the muzzle brake that without covering would send hot lead out and back towards you in recoil. So I only use the cast bullet only muzzle brake in my 460V S&W magnum X-frame revolver. It also shoots jacketed and solid copper bullets just fine. And adds a half inch to the length of the revolver by extending the muzzle brake out in front with a single port. Try it and see.