Originally Posted By madcratebuilder:
The recommended barrel nut torque is 30-50lbft, not to exceed 80lbft.
I agree with this.
Where does this recommendation originate from ?
Anti-seize may cause corrosion on the barrel nut threads, use only a quality molybdenum disulfide grease. You torque the nut three times to 30lbsft to seat the threads, then do the finial tightening.
The Permatex product mentioned above uses aluminum powder which of course is a conductor.
That would be a no-no for the barrel nut.
The idea is to isolate dissimilar metals.
In practice with all manner of products on the barrel nut, including nothing, light civilian duty allows it.
Personally if I do not have gas tube alignment by 50lbsft I well hone the end of the upper about .001 and try again. You don't need to remove much material to get the torque number down to 50lbsft. Tightening the barrel nut to 80lbdft of torque puts undue stress on the upper. I think optimum accuracy would be in the 40-50lbsft of torque, IMHO.
Brownells states that optimum is under 40.