Patriot Ordnance Factory Patriot Ordnance Factory, 308 Triple Port Muzzle Brake, 5/8 x 24 RH, Black Finish 309 Designed by POF this nitride heat treated muzzle brake controls muzzle impulse for ultimate accuracy and an unbelievably soft recoil. Comes complete with a nitride heat treated collar and five (5) strike prongs.