AR barrel nut torque... is 30 ft/lbs enough?

[TTv2]

I know the range is 30 to 80 ft/lbs on the torque, but 30 sounds too low to me, I would rather be somewhere between 40 and 70. A recent attempt using an AR Stoner free float rail and supplied barrel nut ended with it only being able to index the gas tube at 30 ft/lbs of torque, anything more and the tube wouldn't go in.

And yes, I used shims, but wasn't given enough in the box to work with.

I just want to know, for those who build there own uppers, have you ever went with the 30 ft/lb minimum and how'd that go?

 

[someguy2800]

Right or wrong I snug it up and go to the next slot that lines up.

 

[badkarmamib]

The typical rule is 30 ft-lbs, then index to the next notch. If 30 gets you lined up, I would call it good enough. You would probably be over 80 before you got to the next notch, either cracking your receiver, or, at the very least, making it impossible to remove later without causing the same crack. For most applications using a mil-spec barrel nut, the nut won't see much torque from use, and the gas tube itself will keep it from moving much.

 

[JONWILL]

I build most of my uppers anymore. Most don't have the notches. They just use plain barrel nuts that use a normal wrench. I used a torque wrench once. After that it was easy to tell I was over the minimum pressure.
Just make sure you use some lube so there isn't any binding.

I wouldn't have any problems with the 30lb since the gas tube holds the barrel nut in place. If you are worried you can order more shims or file off the top of the notch and crank it down a little more

 

[GBExpat]

Brownell's Take ... Listen to what he says starting shortly after the 1:00 mark:

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=11439

 

[FL-NC]

The typical rule is 30 ft-lbs, then index to the next notch. If 30 gets you lined up, I would call it good enough. You would probably be over 80 before you got to the next notch, either cracking your receiver, or, at the very least, making it impossible to remove later without causing the same crack. For most applications using a mil-spec barrel nut, the nut won't see much torque from use, and the gas tube itself will keep it from moving much.

This is sound advice, and is how I have been doing it for 30+ years. Its has been proven to be sufficient for millions of these guns in the mil. The standard process outlined in the mil is as follows: Torque then release 2 times at 30 foot pounds.This "sets" the threads and removes any galling/imperfections. On the third and final 30 ft lb torque, then begin the process of adding torque as required in order to line up the barrel nut, then align other hardware (D ring, spring, snap ring, etc. if present). The only extra thing I do is prior to beginning the process, I coat the receiver threads with anti-seize, like what you use (or should use) on the threads of spark plugs.Below is a barrel nut I recently removed during a customization project on an AR10 carbine. It was factory installed, and I have no idea how or why the assembler was able to get this thing so tight without damaging the nut, the upper, or both. I was lucky to get the thing off.

 

[LoonWulf]

Right or wrong I snug it up and go to the next slot that lines up.

This is what I do also, tho if I'm under 30, or over 50, I'll usually shim it.

 

[imashooter]

Maybe, maybe not. Index and monitor. You can purchase additional shims of assorted thicknesses easily, to include ebay at times. If you have a belt sander you can remove material from shims as well.

 

[briansmithwins]

30ftlbs on a nut that’s lubricanted is a significant preload.

BSW

 

[1911 guy]

30 foot pounds only sounds "light" until you have to push toward the torque limit to line up the next notch. Then 30 seems mighty fine. Anecdotal evidence indicates that torques nearer the low limit result in better accuracy, too.

 

[Varminterror]

I lap the face of my extensions to yield 35 lbs when indexed. Never needed more than 35, and I only use 35 because it’s NOT minimum spec (30). I fit my barrel extensions, some I even glue in place. The nut doesn’t need to be 65ft.lbs. just to keep the barrel in place.

 

[Schlegel]

I just built an upper and when i timed the nut it took 79 ft lbs to get it right. Maybe that's ok technically but i undid it and shimmed it so it only needed 34-35. The way the S-one forend i used is made it acts as an anti-rotation lock on the nut anyway.

 

[IndianaBoy]

I only use handguards with a barrel nut that allows installation of both the handguard and the gas tube without indexing either one by torque.

 

[MistWolf]

Some experienced assemblers report that about 45 ft/lbs is the sweet spot for precision.

 

[RussellC]

I only use handguards with a barrel nut that allows installation of both the handguard and the gas tube without indexing either one by torque.

Same here. Snug it up, then with crow's foot wrench on torque wrench, set it where ever you want.

Russellc