Barrel nut Torque

[razor]

Hey all you more knowledgeable builders out there, What is the correct torque for the barrel nut?? I have read anywhere from 30 lbs. to 50 lbs.. My Colt manual (CM102) sez 30lbs. WHO's right??? Thank's for Your Help.

[KWP]

I torque to 45 lbs then tighten to bring gas tube in alignment.

[stokesrj]

I had read and believed it was a critical accuracy factor that the barrel nut be torqued to a specific value. However when I went to the NRA school of Gunsmithing at Trinidad Colorado to take a class on building National Match M16/AR15 rifles capable of winning the national match I found out differently. I showed up with my newly purchased Brownells Armorers kit complete with torque wrench. They kind of laughed at me and said why did you go spend all that money. All you need is a set of punches, an armorers wrench, a strap wrench, a hammer, and vice blocks.

The first rifle I built, I torqued it to 35 lbs but a tooth on the barrel nut lined up perfectly centered on the gas tube passageway. The instructor said back it off, and tighten a couple of times and just take it to whatever is required to line it up. I watched my torque wrench go to 80 lbs and that wasn't enough, then 90, and then 95 until it finally lined up. I was sure this would warp the receiver or something but the instructor just chuckled and said don't worry about it.

That Instructor was John Holliger who builds more national match winning AR's than anyone, his rifles dominate the national matches. He is also in the top 20 or so competitors every year at the national matches for the past 10 years of so, is a distinguished rifleman, Presidents 100, and High Master, so he knows.

That rifle shot less than .5 MOA for the life of the barrel and is now on its third barrel. I used it to shoot my personal best national match course in a registered match a 493-27X (485 is high master) so it certainly didn't hurt it to torque the barrel nut to nearly 3X the recommended force.
I later learned that John has two runs of barrel nuts made each time he orders then from Compass Lake Engineering an A and a B batch of 1,500 each. One barrel nut batch is run with one CNC mill setting, the second batch is indexed a half gas tube diameter and run. If the torque required to line it up is greater than 60 lbs or so he goes to the opposite batch, A to B or B to A. John claims it is absolutely not critical if the torque is 30 ft lbs or 60 ft lbs.
I hope that helps your understanding, it is what I learned.
Bob

[Bennybone]

^^^ Good info

The manual for my Mega upper calls for 65 ft/lbs

[Leadfarmer]

I build AR platform guns for a manufacturer and I am with Stokesrj, we just use the mil spec Armorers Wrench. I just tighten it and then line up for the gas tube. That is it!!!!! Never had an issue with any weapons purchased or any of my own. And please don't use lock tight!!!!

[razor]

Thank's for the replys you guy's. Just wondering,the nut for my MI SS hand guard is out of round,won't thread on all the way,lack's 1/8th to mate up. It threaded great before instalation. Thank's Tim

[Allen]

....And please don't use lock tight!!!!

Can I ask why. I've heard diferent stories from different sources, some say lock-tight and some say anti-seize. I personally would think that once you put the barrel on you don't ever want it to move in relation to the reciver (aka, where your optic is mounted), so I was thinking of putting some lock-tight on the barrel and the nut too.

[ricsmall]

[QUOTE=Allen;37445]Can I ask why. I've heard diferent stories from different sources, some say lock-tight and some say anti-seize. I personally would think that once you put the barrel on you don't ever want it to move in relation to the reciver (aka, where your optic is mounted), so I was thinking of putting some lock-tight on the barrel and the nut too.[/QUOTE

thats a big negative! At 60 ft lbs, your barrel nut isnt gonna move. you will need to remove it one day, so dont loctite your nut! use anti seize,as it will keep the threads from galling.

to give you an idea, the bolts that hold the axle on your vehichle are @ 45-55ft lbs.

[seatleroadwr]

Some target shooters recommend loc-tite on the barrel extension to form a gasket between the inside of the reciever and the barrel. Don't use it on the threads though. Use the anti-seize stuff that the guys above recommend.

[wulkyrie]

I had read and believed it was a critical accuracy factor that the barrel nut be torqued to a specific value. However when I went to the NRA school of Gunsmithing at Trinidad Colorado to take a class on building National Match M16/AR15 rifles capable of winning the national match I found out differently. I showed up with my newly purchased Brownells Armorers kit complete with torque wrench. They kind of laughed at me and said why did you go spend all that money. All you need is a set of punches, an armorers wrench, a strap wrench, a hammer, and vice blocks.

The first rifle I built, I torqued it to 35 lbs but a tooth on the barrel nut lined up perfectly centered on the gas tube passageway. The instructor said back it off, and tighten a couple of times and just take it to whatever is required to line it up. I watched my torque wrench go to 80 lbs and that wasn't enough, then 90, and then 95 until it finally lined up. I was sure this would warp the receiver or something but the instructor just chuckled and said don't worry about it.

That Instructor was John Holliger who builds more national match winning AR's than anyone, his rifles dominate the national matches. He is also in the top 20 or so competitors every year at the national matches for the past 10 years of so, is a distinguished rifleman, Presidents 100, and High Master, so he knows.

That rifle shot less than .5 MOA for the life of the barrel and is now on its third barrel. I used it to shoot my personal best national match course in a registered match a 493-27X (485 is high master) so it certainly didn't hurt it to torque the barrel nut to nearly 3X the recommended force.
I later learned that John has two runs of barrel nuts made each time he orders then from Compass Lake Engineering an A and a B batch of 1,500 each. One barrel nut batch is run with one CNC mill setting, the second batch is indexed a half gas tube diameter and run. If the torque required to line it up is greater than 60 lbs or so he goes to the opposite batch, A to B or B to A. John claims it is absolutely not critical if the torque is 30 ft lbs or 60 ft lbs.
I hope that helps your understanding, it is what I learned.
Bob

Sir,
Does Mr. Holliger recommend putting loctite on the barrel extension to bed it (not the threads) for better accuracy? Is this step really necessary? Thank you

[Bill Alexander]

For a GRENDEL build the finished barrel nut torque when everything is aligned should not be less than 60 ftlbs.

We employ Loctite 243 to bed the barrel extension to the receiver. We have the option of running the receiver bore tight and still use Loctite due to the structure of the surface coating on the receiver and also the imperfections that may be present in the barrel extension. With CMM data one finds they are rarely round.

For receiver threads we will employ the same Loctite for assembly. Early work with the cartridge, especially hotter loadings found it is possible to create radial movement of material and flex the assembly. Most times this is not problematic but in mass production one cannot tolerate +10% of accuracy failures due to this effect. Loctite in the threads removes this problem. The grade used is a removable type so anyone proficient with mechanical assemblies will not have problems. The material provides a better long term joint for both durability and also corrosion.

[wulkyrie]

Thank you, most enlightening! But how do you use antiseizing grease and loctite at the same time or no grease at all?

For a GRENDEL build the finished barrel nut torque when everything is aligned should not be less than 60 ftlbs.

We employ Loctite 243 to bed the barrel extension to the receiver. We have the option of running the receiver bore tight and still use Loctite due to the structure of the surface coating on the receiver and also the imperfections that may be present in the barrel extension. With CMM data one finds they are rarely round.

For receiver threads we will employ the same Loctite for assembly. Early work with the cartridge, especially hotter loadings found it is possible to create radial movement of material and flex the assembly. Most times this is not problematic but in mass production one cannot tolerate +10% of accuracy failures due to this effect. Loctite in the threads removes this problem. The grade used is a removable type so anyone proficient with mechanical assemblies will not have problems. The material provides a better long term joint for both durability and also corrosion.

[Bill Alexander]

We do not apply anti-seize compound or grease to the threads. One of the attributes of Loctite is that it acts as lubrication during assembly and when removed will resist thread galling of the components.

[seatleroadwr]

Bill, do you have any trouble removing a barrel from a receiver that has been treated with loctite?

[wulkyrie]

Thanks again

We do not apply anti-seize compound or grease to the threads. One of the attributes of Loctite is that it acts as lubrication during assembly and when removed will resist thread galling of the components.