once you torque a barrel nut to a certain torque and the gas tube cutout isn’t aligned, is it safe to loosen the nut and then retorque to a lower setting for final install?
searched for the answer for about an hour on 3 different days
You are supposed to tighten and loosen the nut 3 times to mate the threads together.
Final torque (from memory) is 30-80 ft-lbs.
yup, i meant after that. I went too far on the 4th pull, can I go back to 40-50ish ft-lbs after near 70?
Hafa Adai! The torque range is from 30-80 ft./lbs. If you feel you need the wrench, set it at 30 ft./lbs and then torque until you hit it. Then mark where the barrel nut is at with a white paint pen. Then I would loosen the nut, remove the torque wrench and then slowly tighten again (I would work the threads several times) first.
Keep tightening until you hit the next spot where the nut will allow you to insert the gas tube. Then put it all together.
hafa nai…
thanks, i’d say the threads are worked and the barrel is seated. i got overeager and was close to 70 ftlbs on that 4th actual pass. so now i’ll set to 30 on the wrench, then just go to the next notch. when it’s all lined up and final, will it be good to go if its under 70 ft-lbs? say in the low 50s, or is that too loose after going up to 70?
not sure if i asked the question the right way
As long as you loosen and re-torque and not simply loosen you are fine. I use my MK 1 MOD 0 arm rather than a torque wrench, but I have also done hundreds of barrels.
I generally aim for the middle of the road when I have to use one. Right around 45-50.
rog’, thanks
great info thanks guys
This…
Go to 30, and then tighten as needed to align gas tube cutout. Final torque isn’t critical as long as it’s over 30 and doesn’t exceed 80.
Great input from IG…
Unlike fasteners… which use a torque to stretch the fitting for tension, the barrel nut on the AR actually “crushes” the upper receiver proboscis onto to barrel extension, this is one of the parts of a very clever design that makes the rifle inherently accurate.
30 - loosen - 30 - loosen - 30 loosen - 30 then line up a notch; this works just fine. As with any torque setting, if you loosen before torquing, you are fine.
What then if you try to reach the next notch, but know you won’t make it once you get near it, remove/replace, and end up at the one before that.
You will have a final tq figure of less than what you once stressed the upper to.
Is this bad?
hypothetically, what if it does exceed 80?
You try a different barrel nut. If that’s not possible you can hone one or two thousandths off the face of the upper.
Personally I don’t like to exceed 60lbft with the barrel nuts.
Doesn’t matter one bit, 81 or 120. I’ve seen dozens of barrel nuts that take a 240 pound trained monkey and a two foot cheater bar to break torque. Set your torque wrench for 30 and go to the next notch.
How exactly do you “hone” the face of the upper receiver?
Yeah… I pulled one off that took 140 ft lb to break loose. Not sure how that translates to its original tightening torque value… but it was snug.
Yes sir this correct.
Don’t go beyond or else you go past the yield point. If you do it won’t torque correctly and the threads will be strecthed permantely.
ETA: Don’t forget to use some high temp anti seize or barrel assembly lube on the receiver, barrel extension and threads.
Go beyond what?
What is the yield point?
Which threads will be stretched permanently?
The yield point is where the threads will stertch permantely. It would probably be over 90 lbs of torque. The hreads on the aluminum receiver extension will stretch first before the steel barrel nut.
You can lap the face of the receiver extension to help line up the notch and also square up the face to make it true. I made one of those tools.
ETA: It makes you sights more near mechanical zero after sighting in is done.
Just went from bad to worse… Time to lock it.
What do you mean by that?