Grease on your barrel nut?

[Caveman Jim]

I just use anti-seize.

 

[HB of CJ]

Lapping the upper receiver front flat squares exactly the face of the receiver where it contacts the barrel extension. They make a hand drill model today that is very quick and accurate.

Also works neat and quick when you torque dry that pesky barrel nut to 40-42 pounds, (compensated) and that more pesky gas tube does not align perfectly. Remove the barrel.

Repeat the honing. Just remove a very little bit. Rebarrel. The barrel gets torqued down heavy in a vise. The upper floats. Retorque the barrel nut. Perfect alignment with proper torque.

You most certainly do not go to the next half moon notch in the barrel nut. The barrel probably will go off and on 4-6 times before absolutely perfect torque with perfect gas tube alignment.

This technique is for building precision rifles. Not needed so much for just piece work assembly jobs. That is all. Enjoy.

Hundreds of builds but now I am old. Yikes!

 

[titsonritz]

I use ARP ultra torque assembly lube. You can tell me there is better assembly lube and I wont believe you.

No reason to ever torque a barrel nut to more than 40 lbf-ft anyway

That depends, KAC URX spec is 45-55 ft.lb., DD RIS II spec is 55 ft.lbs., the military spec per TM 9-1005-319-23&P is 30-80 ft.lb.

 

[wired]

That depends, KAC URX spec is 45-55 ft.lb., DD RIS II spec is 55 ft.lbs., the military spec per TM 9-1005-319-23&P is 30-80 ft.lb.

No advantage to doing that. You arent stretching the threads on the aluminum receiver. 80 lbf-ft is ridiculous. 30-80 isnt even a spec.

 

[HB of CJ]

Another example where the govmnt manuals are wrong. 80 pounds is way way way too too too mucho. You will crack uppers. Do not ask how I know this to be true. More Yikes!

 

[Kruel J]

80 lb/ft? Some upper receiver manufacturer musta started that rumor to increase their sales numbers. And some .gov employee bought it.

 

[Jcon268]

80 lb/ft? Some upper receiver manufacturer musta started that rumor to increase their sales numbers. And some .gov employee bought it.

I've torqued a barrel nut to 80 lbs exactly just to see if anything happened. Nothing happened.

 

[wired]

PSA torques them to 150 with loctite.

 

[Kruel J]

I've torqued a barrel nut to 80 lbs exactly just to see if anything happened. Nothing happened.

Well, I don't think a genie is going to pop out and grant you three wishes. More likely stress cracks, goofed up threads and eventual failure.

I've seen techs use their impact guns to hammer down lugnuts without a problem either. Of course the wheel studs eventually break off so there's that. Just because you can doesn't mean you should.

 

[Kruel J]

PSA torques them to 150 with loctite.

lb/ft? No way.

 

[wired]

lb/ft? No way.

Just seems that way.

 

[Kruel J]

Just seems that way.

Ah lol. I was about to post that Ford recommends that for lug nuts on an F-150. And we ain't talking lug nuts here.

 

[DirectDrive]

I eat a chocolate bar and then spit on the receiver threads.
38 ft lbs and perfect alignment every time.



Hundreds of builds (gone bad)

 

[Jcon268]

Well, I don't think a genie is going to pop out and grant you three wishes. More likely stress cracks, goofed up threads and eventual failure.

I've seen techs use their impact guns to hammer down lugnuts without a problem either. Of course the wheel studs eventually break off so there's that. Just because you can doesn't mean you should.

I honestly expected some distortion of the threads but there was none. I did season the threads three times per the standard. My guess is that had I gone 5 to 10 lbs more, something would have happened. I can't imagine why they would allow 80 lbs if it were cracking upper receivers. On the other hand some AR barrel nuts are different than standard mil-spec and might impart more stress on the receiver than a standard barrel nut. I usually land between 40 and 50 lbs.

 

[Kruel J]

Yeah man 40-50 is plenty.

 

[titsonritz]

Another example where the govmnt manuals are wrong. 80 pounds is way way way too too too mucho. You will crack uppers. Do not ask how I know this to be true. More Yikes!

80 lb/ft? Some upper receiver manufacturer musta started that rumor to increase their sales numbers. And some .gov employee bought it.

I currently have multiple copies of TM 9-1005-319-23&P 25 Nov 1983, May 1991, June 1991 & Nov 2008 (which as far as I know is still the latest) as well the notes I've taken while attending AR Armorers classes and all say the exact same thing. Minimum torque of 30 ft.lb. and do not not exceed 80 ft.lb.

While government manuals may contain errors and/or dated information, like the old ones that had the carrier key screws torque at 35-40 ft.lb. when it should have been 35-40 in.lb., the 80lb max on the barrel nut has been consistent for decades.

And yes I agree, 40-50 is plenty.

 

[titsonritz]

I eat a chocolate bar and then spit on the receiver threads.
38 ft lbs and perfect alignment every time.



Hundreds of builds (gone bad)

Is that milk chocolate or dark bitter sweet?

 

[Jcon268]

I eat a chocolate bar and then spit on the receiver threads.
38 ft lbs and perfect alignment every time.



Hundreds of builds (gone bad)

That's genius. Then when your barrel nut seizes up and you have to break out the torch, you've got a melted chocolate mess.

 

[titsonritz]

Just seems that way.

150 or 15, what a little zero among friends. I've literally seen some hand tight.

 

[coop44]

150 or 15, what a little zero among friends. I've literally seen some hand tight.

Likely it shot just fine too.