The brake I selected for my SPR build, Griffin Armament’s M4SD-II Muzzle Brake, came in the mail today.
As I understand it the US Navy SPR project/Mk18 uses an Ops Inc Muzzle Break. These proved difficult to obtain in Canada and are close to $200 US. I’ve opted to use another Griffin Armament product after being very pleased with the compensator I used in my 11.5″ upper build. Since I can’t buy a suppressor in Canada, muzzle device selection is purely for recoil management.