Abstract: A rifle has an adjustable muzzle brake attached to a muzzle end of the rifle, the muzzle brake including an inner sleeve surrounded by an outer sleeve. The two sleeves are rotatable with respect to each other and have a pattern of holes formed in each. A pair of detent mechanisms formed in the inner and outer sleeves allow the outer sleeve to rotate to a first position with respect to the inner sleeve where the holes of both sleeves are aligned with each other. In this position the gases of combustion can escape through the aligned holes in both sleeves in a substantially transverse direction to the axis of the gun barrel. This provides for a significant reduction in the amount of recoil force on the shooter of the rifle. The detent mechanisms also allow the outer sleeve to be rotatable to a second position where the holes of the inner and outer sleeves are totally out of alignment with each other.