Barrel Nut Torquing?

[Scottyvwork]

Hello, I’m pretty new, on my 4th build and my 2nd grendel. This is the first indexing barrel nut I have used. I have a Gibbz side charge upper a Faxon 12” barrel with Faxon carbon fiber hand guard. My issue is I followed Faxons installation instructions for the barrel nut (35ftlbs twice then up to 80ftlbs to align gas tube).
My problem is that my tube aligns at about 18ftlbs, when I take it up to 80 it’s a half a notch off. What do I do? Thx in advance!

Ps: Is 18 enough?

[Bigs28]

Did your barrel nut come with Shims?

[LRRPF52]

Did you Aeroshell the threads?

When using a toothed standard barrel nut, I go by feel and align.

You can also Dremel off one of the teeth if you want to stick to an arbitrary ft-lbs torque spec for the barrel nut.

AMU fleet tested this to see if there were any benefits to torque value vs accuracy, and found that heavy barrels did better with 40ft-lbs, while government profile barrels grouped better with 80ft-lbs.

Torque can have a damping effect on harmonic resonance, but that’s in the weeds for accuracy enhancing techniques.

Make sure your receiver face is square too.

[montana]

I use barrel shims, they are quite easy to use..

You need to make sure you grease the the threads as 52 explained.

Lightly grease the front of the barrel flange the shims rest against (between the barrel flange and barrel nut face) front side.

Be sure to lightly grease both sides of the shims.. Installing shims dry can damaged them during the barrel nut torque process..

[Klem]

Scotty,

Unusual that in 18-80lbs a gap does not line up for the gas tube. I have heard of people going to 85lbs but don't go any higher or the aluminium will start to deform.

For something as important as the barrel-receiver interface I would stick carefully within the recommended range 35-80lbs. I cut off a tooth once and it worked. You don't need all 20 teeth to get the barrel nut on and off, and they are only there to aid assembly. One missing tooth will do absolutely nothing to anything, except let you fit that gas tube properly. Plus, you won't see the missing tooth once the handguard goes on.

As for what torque, 35-40lbs is what manufacturers of non-teeth handguards are recommending, but not less than 35lbs - and definitely not 18lbs.

[Bonas]

I'll add one more vote for cutting a tooth.

[montana]

https://bisonarmory.com/ar-15-barrel-nut-shim-set/

https://www.primaryarms.com/aero-precisi...-shim-pack


Having to spend a little over $5.00 for barrel shims to properly torque and align the barrel nut is worth it to me, instead of doing a bubba job and mangling the barrel nut on a $300.00 + carbon fiber hand guard, but hey, that is just me...

[Scottyvwork]

Thanks for all the advice, given me some good options!
ScottyV

[BlogSarge]

add another vote for facing the front of the receiver to assure it is square. This could gain you the needed extra bit of rotation of the barrel nut.

[montana]

add another vote for facing the front of the receiver to assure it is square. This could gain you the needed extra bit of rotation of the barrel nut.

Be sure when facing (lapping) the front of the receiver the barrel extension feed ramps don't extend too far over the uppers feed ramps or you will need to do barrel feed ramp work...

[Bonas]

It's not about the cost of shims. It's about the fit between the receiver face and the the barrel extension. I would rather drop a tooth off the nut than put a shim in there. Based on my own testing and experience, the extension to receiver fit is worth about .25 moa. I shim the extension with stainless stock to achieve a press fit, after checking squareness. I think what's happening inside is more important than what it looks like outside. YMMV.

[Bonas]

It's not about the cost of shims. It's about the fit between the barrel extension flange and the receiver. I wrap extensions with stainless stock to achieve a press fit between the extension and the receiver tube. From tearing down uppers and reassembling them, I find this improves accuracy by about .25 moa. I don't care what the barrel nut looks like under the handgaurd. Based on my experience, I would not want a shim between the receiver face and the extension flange, if I could avoid it. I would rather cut off a tooth. In fact, I prefer handguards with nuts that don't have to be timed for this reason. For what it's worth, I have rifles that have shims between the nut and the receiver, but I prefer otherwise. YMMV.

[montana]

It's not about the cost of shims. It's about the fit between the barrel extension flange and the receiver. I wrap extensions with stainless stock to achieve a press fit between the extension and the receiver tube. From tearing down uppers and reassembling them, I find this improves accuracy by about .25 moa. I don't care what the barrel nut looks like under the handgaurd. Based on my experience, I would not want a shim between the receiver face and the extension flange, if I could avoid it. I would rather cut off a tooth. In fact, I prefer handguards with nuts that don't have to be timed for this reason. For what it's worth, I have rifles that have shims between the nut and the receiver, but I prefer otherwise. YMMV.

The shim does not go between the upper's receiver face and barrel flange, it goes between the barrel flange and barrel nut..This is why it is important to grease the front of the barrel flange and shims..

Putting the shim between the upper receiver and barrel flange can change the lock up timing/indexing, gas tube depth into the gas key and create other problems..

I assumed this was common knowledge. This is what I get for assuming things..

[Klem]

The shim does not go between the upper's receiver face and barrel flange, it goes between the barrel flange and barrel nut..This is why it is important to grease the front of the barrel flange and shims..

Putting the shim between the upper receiver and barrel flange can change the lock up timing/indexing, gas tube depth into the gas key and create other problems..

I assumed this was common knowledge. This is what I get for assuming things..

Montana,

On the Bison link video the shim is being inserted between the receiver and barrel extension. He snips his shims to do this.

Regardless, using words like ‘Bubba’ and ‘mangle’ are freighted with the assumption we don’t know what we are doing. As I wrote, I’ve removed a tooth before and it works. I’m with Bonus on this one. Why risk the critical receiver-extension interface for the sake of lining up the gas tube. Alternatively, removing a tooth preserves the interface and is easier and cheaper.

Note also in the video he only torques to 30ft lbs and not up to 80. That acceptable MILSPEC range could align the tube without needing to buy his shims.

[montana]

Montana,

On the Bison link video the shim is being inserted between the receiver and barrel extension. He snips his shims to do this.

Regardless, using words like ‘Bubba’ and ‘mangle’ are freighted with the assumption we don’t know what we are doing. As I wrote, I’ve removed a tooth before and it works. I’m with Bonus on this one. Why risk the critical receiver-extension interface for the sake of lining up the gas tube. Alternatively, removing a tooth preserves the interface and is easier and cheaper.

Note also in the video he only torques to 30ft lbs and not up to 80. That acceptable MILSPEC range could align the tube without needing to buy his shims.

Mangling a barrel nut when not needed is not considered quality work where I'm from Klem, but people do have different standards.. If you purchased a new rifle and the manufacturer ground off one of the keys to reach torque spec I'm sure you would be A-OK.. I wouldn't be, I would ask for a refund....

I did watch that video a while ago before they turned off the comment section for a reason.. Putting shims between the upper receiver and the barrel flange, is doing it wrong..

I know all about your opinion on quality work, such as shooting questionable loads from behind a tree, sand papering the boat tail to remove carbon and grinding out the aluminum upper receiver feed ramps while simultaneously removing the hard anodizing in the process..

One thing I do know is there can be a lot of contention between AR building procedures between the so called experts..I know I don't agree with any of them 100% of the time, even those I respect the most.... I just take it with a grain of salt when certain people get triggered by mine or other peoples opinions..What I call Bubba work you and others may consider top notch gunsmithing.. That's whats great about the USA, having an opinion and the right to choose who we listen to..In either case it is no skin off of my teeth what you or others do with their rifles, I'm not in a popularity contest or care what the latest consensus is..People ask for opinions and I give them mine.. They can choose who they wish to listen to or not.. Have a great day Klem..

[Klem]

OP,

The way I see is you can cut (not mangle) off a tooth, or use a shim on the back (not front) of the extension flange. Unsure whether rotational torque on the shim when doing up the nut will distort anything I don’t imagine so.

As for demanding a refund if encountering a missing tooth I’d know why, especially given as the missing tooth would be at the gas tube. If it was a gunsmith I had commissioned then I’d have a chat about it before going nuclear. I build my own guns so it’s all hypothetical. I prefer hanguards with proprietary nuts that clear the gas tube. Yes, we have a different approach to these things but I don’t compromise reliability or accuracy. Same outcome, different ways to achieve it - by all means talk-up your techniques but be careful not to include the other person when discrediting theirs.

[montana]

OP,

The way I see is you can cut (not mangle) off a tooth, or use a shim on the back (not front) of the extension flange. Unsure whether rotational torque on the shim when doing up the nut will distort anything I don’t imagine so.

As for demanding a refund if encountering a missing tooth I’d know why, especially given as the missing tooth would be at the gas tube. If it was a gunsmith I had commissioned then I’d have a chat about it before going nuclear. I build my own guns so it’s all hypothetical. I prefer hanguards with proprietary nuts that clear the gas tube. Yes, we have a different approach to these things but I don’t compromise reliability or accuracy. Same outcome, different ways to achieve it - by all means talk-up your techniques but be careful not to include the other person when discrediting theirs.

No, the shim goes in the front, not the back of the barrel flange which serves no advantage and can be detrimental..Doing so to a trued (lapped) receiver front is counter productive and detrimental..But like I stated before, what you and others do with your rifles is no skin off of my teeth..

I have yet to see a Colt or any other factory rifle where they cut a barrel nut key to obtain proper torque..If a gun smith recommended cutting a barrel key, (I wouldn't go nuclear lol), but I would say have a nice day and try to find a competent gunsmith....

I never mentioned anyone's name Klem, so I don't know what you are talking about discrediting them..I will discredit (methods) I believe to be wrong, detrimental or even harmful, with or without your approval..You and others are obviously free to discredit my opinion without needing my approval.. That is what is called discussion..

So what I'm confused about is why are you trying to set ground rules for me if not blatantly giving me a warning?? If this is the direction you are taking, you are barking up the wrong tree..

[Klem]

Montana,

I think we might be getting the front and back of the barrel extension mixed up. I understand you are recommending Bison shims, but not their recommended assembly - if so, then we agree. I would think putting the shim on the muzzle side of the extension would be better. As long as the shim does not gall as you crank up the torque, and a bit of lube would solve that.

[montana]

Yes, we are in agreement on shim placement and they can gall if not lightly greased..

I just posted some inexpensive shims and I'm not endorsing any brand. My point was there is no need to mangle (grind off the barrel key) when using an inexpensive shim is easy to use..

I have used many different types of shims and they all worked fine. They can be obtained in different thicknesses..

We obviously disagree on many methods and I have no problem with that..I will speak my mind as I would expect you to.. I do have a problem when it starts to turn into a chest pounding exercise which I have no desire to participate in..

I'm sorry if I upset you Klem, it was not my intention..

Have a nice day..