AR Barrel Nut tension why some manufactures say 30 others 50 some 55 ft pounds

[BobbyJ]

I've read a few posts on this topic and in the end and I still don't know if it matters.

On newer uppers there is no gas tube notch to align so the torque can be what ever torque you choose. Some companies say 35 pounds others say use 50 pounds and some others say 55 pounds.

Do they just pull the number out of a hat as it does not matter as long as its something between 30 and 80? Lets say the manufactures says 55 pounds but you set it at 40 pounds. What is the harm? The barrels i not going to fall off at 40 pounds.

Anyone know the logic behind so many different recommendations?

 

[akajun]

Doesnt really matter, as long as its tight enough to not come off.

What Ive found does matter
cleaning and putting anti sieze on the barrel nut threads
making sure the gas tube is aligned and enters the upper straigt not touching a tooth on the nut that pushes is to the side and doing the same to the bolt carrier.
Good fit on the extension and the upper, making sure the upper face is flat and the ID and OD are snug. This can be tightened up with a shim if needed

 

[Mr. Ten-X]

I have yet to lay a torque wrench on a barrel nut. As above, I use an anti-seize compound on the threads and give it a solid twist. I use shims if appropriate to achieve a good torque.

 

[Jeff Porter]

German torque … Gutentite

 

[1raggedhole]

There must be something to it. WOA makes the best out there and they torque even higher, apparently for a reason. Make it super tight with loctite.

 

[Walt Krafft]

I slather everything with BLUE Loctite and tighten it until it is snug and the gas tube alignment is perfect to the bolt carrier key. Then let it sit for 24 hours to let the Loctite do its thing. Never had a problem getting one appart after a little heat was applied. The Loctite fills any gaps and voids if the fit is a little sloppy.

 

[Herzo]

Clarification of akajun's comment, insure the face of the upper receiver ts square to the bore. A lap for that purpose is available.

 

[BobbyJ]

I slather everything with BLUE Loctite and tighten it until it is snug and the gas tube alignment is perfect to the bolt carrier key. Then let it sit for 24 hours to let the Loctite do its thing. Never had a problem getting one appart after a little heat was applied. The Loctite fills any gaps and voids if the fit is a little sloppy.

I thought you were suppose to use anti seize/gall grease and no licktite on the threads.
Not saying its wrong there is more than one way to do the same thing.

 

[BobbyJ]

Clarification of akajun's comment, insure the face of the upper receiver ts square to the bore. A lap for that purpose is available.

That is not easy to to on a Aero Enhanced upper. Its encased in the monolithic extension that holds the hand guard. On a standard AR upper yes that is easy to verify.

 

[BobbyJ]

I have yet to lay a torque wrench on a barrel nut. As above, I use an anti-seize compound on the threads and give it a solid twist. I use shims if appropriate to achieve a good torque.

The barrel company said the same thing, they just snug them up tight and not worry about torque settings.

I'm not sure anyone has ever tested that it even matters.

10 pounds - maybe the barrel wiggles or can be rotated (too loose)
25 pounds - No idea might be good enough
30 pounds - Seems the military found this to be fine
40 pounds - same
50 pounds - same
60 pounds - same
70 pounds - same
80 pounds - same
90 pounds - start to maybe stress the threads too tight or getting there.

I've not read one logical reason why to use 50 pounds over 40 pounds or vise versa One person said 50 is the goldilocks amount which to me makes no sense.

 

[Coyotefurharvester]

I used a Lantac spada-s for my 20p build. It calls for 70-75 ft lbs. I had several poi shifts during load development that gave me trouble. I had my garage torque wench checked, it was only loading 32# at the 75 setting after calibration I pulled the upper apart and reassembled. Have not had any issues since torqued to Lantac specs. I did check the torque the old way(dead weight/with lever).

 

[BobbyJ]

I used a Lantac spada-s for my 20p build. It calls for 70-75 ft lbs. I had several poi shifts during load development that gave me trouble. I had my garage torque wench checked, it was only loading 32# at the 75 setting after calibration I pulled the upper apart and reassembled. Have not had any issues since torqued to Lantac specs. I did check the torque the old way(dead weight/with lever).

There we go! So in your case 32 pounds (wow that wrench was way out of spec) maybe the lower limit was not as good as 75 pounds. But maybe 40 or 50 was fine.

Appreciate the info. But was your upper mil-spec or a proprietary upper?