08-11-2011, 03:44 AM
The standard for AR15's is usually between 30 and 80 foot pounds, but the barrel nut teeth really are the determining factor, since they need to be lined up for the gas tube, unless you're using a unique barrel nut without teeth.
What is recommended by armorer courses is to tighten up to the torque setting, then back it off, tighten again, and tighten to index the barrel nut teeth so that the notch is perfectly aligned for the gas tube.
Something seems to trigger my memory that I read on the old forum that it was better to go a little higher than 30 foot pounds with the Grendel, but I could be wrong. Over 80 foot pounds will crush your threads on the aluminum upper, so I would stay in between.
After building so many AR's using the torque wrench, and seeing how it really didn't matter compared to what I thought tight should be, plus the gas tube alignment, I just feel what should be right, and don't worry about it. I still tighten, then loosen 3 times to settle the barrel nut threads with the upper receiver extension threads, but the gas tube really drives this procedure.
Just make sure you insulate your upper with plenty of thick tape, even if you're using an upper clamshell in your vice. The plastic will still make marks on the anodized surface, and looks tacky...if you care about such things.
What is recommended by armorer courses is to tighten up to the torque setting, then back it off, tighten again, and tighten to index the barrel nut teeth so that the notch is perfectly aligned for the gas tube.
Something seems to trigger my memory that I read on the old forum that it was better to go a little higher than 30 foot pounds with the Grendel, but I could be wrong. Over 80 foot pounds will crush your threads on the aluminum upper, so I would stay in between.
After building so many AR's using the torque wrench, and seeing how it really didn't matter compared to what I thought tight should be, plus the gas tube alignment, I just feel what should be right, and don't worry about it. I still tighten, then loosen 3 times to settle the barrel nut threads with the upper receiver extension threads, but the gas tube really drives this procedure.
Just make sure you insulate your upper with plenty of thick tape, even if you're using an upper clamshell in your vice. The plastic will still make marks on the anodized surface, and looks tacky...if you care about such things.