Gunsmithing should i loctite the barrel extension and other good knowledge please

[Smokerroller]

Alright so I will soon be installing my noveske barrel to an upper. I want my install to be as good as possible to optimize the noveske barrel. I have searched and read and unless I am directed otherwise here, I will do the following. Red loctite on the barrel extension but NOT on any threads. Antisieze on the barrel nut threads. I have read that best accuracy is found with the barrel nut torqued as low as possible. My torque spec range is 30-50 ft lbs on the hanguard's proprietary nut so I will aim for as low in that range as I can. If I am wrong on these or if there is any other extra procedure please let me know. I want every bit of accuracy out of this setup as I can get. Thanks.

Also it will get ceracoated. Are there certain areas it should stay off of?

 

[thebolt]

I have been through one AR armorer school so I am not an expert on this specific issue. I would personally be very hesitant to use the locktite.

Lets see what those with more experience have to say.

 

[msalm]

I discussed this with an Army equipement specialist years ago about the time we started fielding the M110, and he stated to me that Knight ended up 'bedding' or epoxying the barrel extensions in the uppers just as you describe in order to meet the accuracy requirements. I had been building many AR's before that and was using the red locktite as you mention and it's worked well for me. I would take care to lap or face the upper before doing so also to ensure a good square fit. AR's are funny though, you do everything right on them and they typically shoot extremely well, and you just slap one together in haste and the SOB shoot's lights out...not every time by any means but....

 

[MrMarty51]

If there is heat involved locktite`ll melt down and have minimal holding properties.

 

[msalm]

It's not so much the holding property of the locktite that helps IMO, but the filling any gaps and creating a better fit that would have less tendency to shift between shots. I've replaced a few barrels years after locktiting them and believe me, that shit still had a good hold. Most of the heat is forward of that extension surface in the throat area and forward. If it's a precision AR I don't expect barrel-burning temps of course most of my AR's are built for hunters and don't see more than a few hundred rounds/year with the exception of the prairie dog guns.

 

[MrMarty51]

It's not so much the holding property of the locktite that helps IMO, but the filling any gaps and creating a better fit that would have less tendency to shift between shots. I've replaced a few barrels years after locktiting them and believe me, that shit still had a good hold. Most of the heat is forward of that extension surface in the throat area and forward. If it's a precision AR I don't expect barrel-burning temps of course most of my AR's are built for hunters and don't see more than a few hundred rounds/year with the exception of the prairie dog guns.

Now that is a nice explanation of a different sort of use for Lock-Tite. I had`nt thought of it as a filler before, but only as a thread locking solution, Not thinking "Outside the Box" I guess. LOL
I have never built a rifle of any sort, usually find them from individuals, clean them up and use them for whatever purpose I intended them for.
I do want to get one of those Poly80% lowers though and start with that. I would actually like to get a poly80 in the AR10 and install a .243 upper on it, I like the .308 but I think I like the .243 just as much, no money for any of that now though, probably be a few years before I can afford any purchase of any kind. I might though, go ahead and get the AR15-80% just to have it for the just in case there is new restrictions comes out. Know what I mean. LOL

 

[Strykervet]

No loctite! Anti-seize, lithium grease (what military manual calls for IIRC) or CLP or my favorite, TW-25B. I forget which high end manufacturer told me they use TW-25B grease too. JP Ent.?

I don't even use a torque wrench (well, for barrels) but I've worked on enough to know what I'm looking for. SF gunsmith I knew didn't use one either, and to me that guy was the end-all, be-all of weapons knowledge. Basically that damn hole will only line up for the gas tube AND be tight at the same time (without damaging the upper). It's also why the torque range is so damn large, and if the tolerance is that wide I'm not so sure I need precision instruments. But if you have one, go ahead and use it, but it won't be the torque scale you'll be paying attention to, it'll be that gas tube port.

Having a damn good barrel accounts for about 90% of your accuracy with an AR (maybe more). If you use even decent milspec parts for the rest, provided barrel/bolt are GTG, there won't be much you can do to affect accuracy.

 

[Strykervet]

It's not so much the holding property of the locktite that helps IMO, but the filling any gaps and creating a better fit that would have less tendency to shift between shots. I've replaced a few barrels years after locktiting them and believe me, that shit still had a good hold. Most of the heat is forward of that extension surface in the throat area and forward. If it's a precision AR I don't expect barrel-burning temps of course most of my AR's are built for hunters and don't see more than a few hundred rounds/year with the exception of the prairie dog guns.

Yeah, but grease does the same thing and it's made for heat. It still follows the rules of fluid mechanics, which basically states it isn't compressible. This means anything of that nature will do the same, ie, "fill in the gaps".

Grease, loctite, etc., also changes the torque specs due to this, but you don't hear it often. USO will tell you this about their scope rings, and it reduces the torque significantly.

 

[msalm]

I'm not talking about using locktite on the barrel nut and threads on the receiver, only on the surface of the barrel extension that slips into the receiver. I use moly grease on the threads. The locktite has absolutely no affect on any torque that is applied to the barrel nut. Red locktight is a stud and bearing formula...as in a cylinder fitted into a hole....kinda like a barrel extension in the upper receiver. As for a torque wrench, you are correct as they are not needed one bit, there's pretty much only one spot that nut is going to align with a reasonable torque. Some will be a little loose on one and too damnded tight getting to the next though and on those I will either take a few thou off the receiver face with a facing mandrel on the lathe or I'll face off the inside of the barrel nut shoulder a few thou. to get a reasonable torque and proper alignment.

 

[Smokerroller]

Thanks msalm and stryker.I am aware of the torque changing properties of different fluids due to my time as a heavy equipment mechanic. Why not get the barrel nut torqued to say.. 35 lbs to account for your choise of thread compound and then mill out a spot for the gas tube if need be. I also have to get the nut to line up for the handguard to be true with the upper. Thanks guys. Any more good info out there?

 

[kl3309]

I've had better luck with the blue loc-tite versus the red for filling up a bit of tolerance like what you're wanting to do. My experience has been that the blue wicks into gaps a bit better, sets up a lot faster, and is a lot harder when cured. I've had the red stuff not cure at all remaining fluid even after several days.

 

[damoncali]

I've only ever assembled one AR, but there was no gap to fill. The extension was a very close slip fit - probably .001" or less clearance if I had to guess. Is that not normally the case? I find it hard to believe a thin layer of loctite is going to do anything, but am willing to be shown the error in my ways...

 

[flatland1]

I've used #242 blue low-medium strength loc-tite on the outside of the bbl extension to get a better fit in the upper receiver, and found that it's not particularly difficult to remove the bbl from the upper later. Not sure that'd be the case if #272 red loc-tite were used - and don't intend to try it to find out!

Some of the uppers I've seen more recently are a tight fit to any of the M4-type bbl extensions I've got - so tight that I'd guess none of the loc-tite would still remain on the bbl extension after it'd been inserted into the upper. In this case, I wouldn't bother using anything on the outside of the extension.

 

[Ballista One]

There is zero data that supports an accuracy improvement using Loctite on the barrel extension or a correlation between barrel nut torque and accuracy, none. If you grease and pre-stress the threads on the upper receiver, torque the barrel nut to 30 ft lbs and then continue to tighten to the next notch, you will rarely exceed 80 ft lbs of torque. Even if you do, a properly manufactured 7075-T6 forged upper receiver is strong than a bulls balls. I have personally tried twice to rip the threads off of an upper receiver with no luck. Both resulted in barrel nut failure.

Using Loctite on the barrel extension is one of those "mods" that woodshed gumsmiffs used to sell as accuracy magic. The mod has morphed into one that is used by the masses because there is simply very little they can do their rifle that contributes to a true accuracy improvement on the platform.

 

[bptactical]

There is zero data that supports an accuracy improvement using Loctite on the barrel extension or a correlation between barrel nut torque and accuracy, none. If you grease and pre-stress the threads on the upper receiver, torque the barrel nut to 30 ft lbs and then continue to tighten to the next notch, you will rarely exceed 80 ft lbs of torque. Even if you do, a properly manufactured 7075-T6 forged upper receiver is strong than a bulls balls. I have personally tried twice to rip the threads off of an upper receiver with no luck. Both resulted in barrel nut failure.

Using Loctite on the barrel extension is one of those "mods" that woodshed gumsmiffs used to sell as accuracy magic. The mod has morphed into one that is used by the masses because there is simply very little they can do their rifle that contributes to a true accuracy improvement on the platform.

^^^^this.
Imho you are curing a non existent problem. By using a quality upper and barrel the barrel should be a snug slip fit to light press fit into the receiver ring.
I as well have seen no data supporting varying barrel nut torque/accuracy claims.
I have Devcon'd a couple of barrels into the receiver ring for customers at their request on match rifles but they consider the upper/barrel assembly a disposable unit.
True up the face of the ring, observe proper assembly procedures and shoot the thing.
With quality components and proper assembly the machine will be far more capable of accurate work than the human operator is typically.

 

[Billiam1211]

Don't loctite the barrel extension. I learned this lesson the hard way, but it wont give you any added benefit over a square receiver face and a properly torqued down barrel nut.

 

[Rocketvapor]

I'm not going to evaluate the increase/decrease of holding force of a bolt/nut (that's what an upper connection is) with some parts aluminum and some parts steel throughout the expected temperature range.
It happens in the aerospace industry (rocketships) and needs to be considered.
My "Guess" is some engineer determined a minimum torque and a maximum torque based on something other than accuracy. If that is the case then just about anything within the range of torque will hold and not over stress the parts.

Now, about filling the gap. A slip fit, even a tight slip fit has some give. Fill it with a product that has some give might feel good but under firing loads does it give?
The steel shim, thermal fit sounds good.
I use a slightly different approach.
Spray on high temperature paint on the extension, masking the flange off.
I think it's possible to apply a thin, somewhat uniform 0.001 to 0.002" coating, burnishing it smooth, chilling/heating for a thermal fit then assemble. Paint doesn't have the compression strength of stainless steel shim stock.
I feel lapping and shimming creates a more solid joint.
Heavier uppers add a little resistance to flex.
It's that two inches or so in length around the joint that is the basis for upper stability.

 

[JWG]

Alright so I will soon be installing my noveske barrel to an upper. I want my install to be as good as possible to optimize the noveske barrel. I have searched and read and unless I am directed otherwise here, I will do the following. Red loctite on the barrel extension but NOT on any threads. Antisieze on the barrel nut threads. I have read that best accuracy is found with the barrel nut torqued as low as possible. My torque spec range is 30-50 ft lbs on the hanguard's proprietary nut so I will aim for as low in that range as I can. If I am wrong on these or if there is any other extra procedure please let me know. I want every bit of accuracy out of this setup as I can get. Thanks.

Also it will get ceracoated. Are there certain areas it should stay off of?

-Noveske uses 50 ft-lb on the barrel nut, at least, back in John's day, although things may have changed, 50# isn't a bad number.

-The barrel extension fitment should ideally require a tiny bit of heat to the receiver, then thermally fitted in. If you have a slip fit, without heat, I also would not really care. If the fitment is like a hotdog in a hallway, you need to get better parts. I'm in the "either thermally fit it, or don't, but don't try putting a bunch of potions in there with it. It is either made correctly, or it's not, and anyways the performance difference is minimal, if any."

-Stay off of the threads, stay off of the ID of the barrel/rec area. Cerakoating blows critical clearances because of the surface prep.

Just my .02. I'd be more worried about the muzzle device than any of this other stuff, honestly. "none" would be best, second that, minimal torque here, if running a suppressor and using 1/2-28 threads, that means 20 ft-lb and Rocksett. If not running a can, hand-tight with Rocksett (optional, depending on if you plan to keep an eye on it or not) for a FH, and experiment with what works for your brake, although I'd be inclined to just to 20.

 

[ShooterwithNoName]

I have always used the same Aeroshell anti-sieze on the extension and threads. Use a barrel clamp on the barrel, run the nut down tight and break it back loose 3 times then final torque ends up about 40ft/lb.

Squaring the receiver face is the only accuracy mod I do to the upper. I will also take a very small piece of soft solder and "bed" the upper and lower together at the front take down pin. Just snip a small piece of solder, then close the receiver halves together and it takes up any gaps or rattle.

 

[357Max]

Alright so I will soon be installing my noveske barrel to an upper. I want my install to be as good as possible to optimize the noveske barrel. I have searched and read and unless I am directed otherwise here, I will do the following. Red loctite on the barrel extension but NOT on any threads. Antisieze on the barrel nut threads. I have read that best accuracy is found with the barrel nut torqued as low as possible. My torque spec range is 30-50 ft lbs on the hanguard's proprietary nut so I will aim for as low in that range as I can. If I am wrong on these or if there is any other extra procedure please let me know. I want every bit of accuracy out of this setup as I can get. Thanks.

Also it will get ceracoated. Are there certain areas it should stay off of?

The best solution would be to use a BCM thermal fit upper. You can buy seconds direct from them for $59.00.
Then true the face of the upper were the barrel extension meets it. Brownells has a reasonably priced kit for this.

You didn't mention it, but buy a Go guage and check head space. Make sure to remove the ejector from the bolt when checking.
No need to buy all three gauges, just the go. If it passes go then add a piece of clear scotch tape to the back of the go gauge and re-check, it should not close with the tape added. It's usually the BCG that causes problems with head space and usually its the coated ones. Specifically thicker coatings like nickel boron.

If not using the BCM then it depends how loose the slip fit is.
Like others I've taken a master AR Armorers class, but what I suggest is my informed opinion. Take it or leave it.

Do not use Red or Blue Loctite.
Yes they may work, but the correct one to use is Green 620 Bearing mount Loctite & it should really be used with Loctite SF 7649 primer if you want to do it right. The Green is rated for a higher temp and is designed to fill small voids.

I have built several with VLTOR uppers. They are quality thick walled uppers, however they have been a loose fit to all the std size barrel extensions I've tried. How loose.........well I was able to assemble one with .001 stainless shim stock 2/3 rds the way around the barrel extension. I Use the 620 Loctite with primer on the loose fit uppers + shim stock if it fits.

See Joe Carlos video below

Edit: The oversize Bat extensions are out of stock and have been for over a year.

 

[357Max]

He is another video where he gets into barrel nut torque at about the 6 minute mark.
He gives good torque targets based on a crap load of testing.