Barrel Nut for AR15 & M4
This is Mil-spec barrel nut used to tighten barrel into upper receiver. This barrel nut is required for Armanov hand-guard. It should be tighten between 30 ft-lb (40 Nm) and 80 ft-lb (108 Nm). Basically you tighten the barrel that passes 30ft/lb torque and allign next possible notch, but torque should not exceed 80ft/lb.