AR Sponsor
Joined:
Jun 2025
Posts:
4
EE: 0% (0)
IL, USA
Posted: 2/7/2026 10:47:42 AM EDT
| OK this may be a matter of personal preference but when installing the barrel on an AR I see some use Aeroshell on the receiver threads only, some use Aeroshell on the threads and barrel extension and some use a high temperature Loctite (I forget the number/ type of Loctite). So what is recommended? Ask the barrel maker? |
|
Grease the threads. Some people will claim Aeroshell is the only acceptable option...but I wouldn't obsess about it. Use a decent grease and you will be fine. The concept is to prevent galling the threads and to get a more accurate torque. Aeroshell isn't some sort of special ninja juice, it just happens to be milspec because Shell is a government contractor. There are plenty of other brands that will do the job just fine. Some will put green loctite between the barrel extension and the receiver to bed the barrel. It is highly debated, but some say it can help minimize play between the two and theoretically improve precision, but it will make removing the barrel more difficult in the future. Loctite doesn't belong anywhere near the barrel nut threads themselves, though IMO. |
|
A dab of AreoShell on the threads is recommended, but any good quality hi-temp grease or anti-seize is a reasonable substitute. Many lower price manufactures don't use anything, and that isn't as big a deal as some people try to make it. I bought 2 oz of AeroShell on eBay, a full tube of it would have lasted me two life times. |
|
Old Bushmaster/Windham Weaponry used motor oil on the receiver/barrel nut threads... I prefer moly grease or moly paste. Grease should be applied to the receiver threads (some grease on the barrel nut threads doesn't hurt either) and the FSB/gas block facing side of the barrel extension flange. |
Joined:
Jun 2025
Posts:
5
EE: 0% (0)
IL, USA
|
Originally Posted By Rkangel777: Grease the threads. Some people will claim Aeroshell is the only acceptable option...but I wouldn't obsess about it. Use a decent grease and you will be fine. The concept is to prevent galling the threads and to get a more accurate torque. Aeroshell isn't some sort of special ninja juice, it just happens to be milspec because Shell is a government contractor. There are plenty of other brands that will do the job just fine. Some will put green loctite between the barrel extension and the receiver to bed the barrel. It is highly debated, but some say it can help minimize play between the two and theoretically improve precision, but it will make removing the barrel more difficult in the future. Loctite doesn't belong anywhere near the barrel nut threads themselves, though IMO. FPNI. |
*Hold on to your AR-15s. Their magic must be very powerful, or they wouldn’t want them.*
JAFOM.... Just another fat old man.
________________________________
TOGC,IADC
JAFOM.... Just another fat old man.
________________________________
TOGC,IADC
Joined:
Dec 2025
Posts:
61
EE: 0% (0)
TX, USA
|
I bought some of this stuff at an auto parts store. Not so much it may lay around taking up space and close to the specs the Gov. used. Separates some if left unused for a year or more and the tube may need to be kneaded to remix. https://www.crcindustries.com/constant-velocity-cv-joint-grease-4-wt-oz/ I would not use a grease that was not listed as a high-pressure grease. I want the grease film to stay in place under use and the connection not possibly loosen. |
|
I use a tiny drop of silver anti- seize and torque to 40 foot pounds and have never had a problem with a barrel galling or loosening up. Don't overthink it. |
Can't believe I actually said "scrotum lady" out loud. - Agent Funky
Zero to DeeJ in about 5 posts. - Troutman84
Zero to DeeJ in about 5 posts. - Troutman84
|
Originally Posted By anesvick: I use a tiny drop of silver anti- seize and torque to 40 foot pounds and have never had a problem with a barrel galling or loosening up. Don't overthink it. A real professional there if the silver stuff stays in one location instead of distributing itself onto everything nearby. It is all about will the film stay in place under the pressure. I can say I did many with silver type anti seize and they all came apart many years later without any issue. No easier and no harder than a typical barrel nut connection should. |
|
May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! 
|
...Amongst the 1911 poors...
|
Originally Posted By m4nut: May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! From what I recall, the torque specs for the barrel nut is actually a range, not necessarily one specific value. I think it’s between 35 and 70 ft lbs. How much beyond 40 ft lbs do you need to go to get it lined up? If it’s not more than 70 ft lbs, my opinion is your are good. |
|
Originally Posted By m4nut: May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! Well, I don't have a lot of experience with this issue but the way I solved this issue in the past is with shims. The other way that I have never tried is to square the upper receiver barrel mounting face to the flange of the barrel extension. A lot of different ways of doing this but many say that sending out the upper receiver to someone that knows what he is doing with a lathe is the way. There are manual tools you can use that may or may not be the best way to do this. There may be other ways too. I have heard that tightening the barrel nut to 80 ft-lbs then loosening the nut all the way and doing this at least 3 times may have a slight effect on getting your barrel nut aligned with the amount of torque you desire. I have not experienced any difference in barrel nut alignment when I have done this. |
Joined:
Nov 2022
Posts:
255
EE: 100% (28)
USA
|
Originally Posted By m4nut: May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! If you’re using the GI barrel nut, the torque range is 30-80 foot pounds. I’ve had a few over the years I probably had to bump a touch over 80 to get alignment and it’s not a big deal. Guns ran well and when disassembled later there were no signs of damage. As long as you’re not using PSA breaker bar levels of torque I wouldn’t worry personally. Otherwise your only other options are to try and shim the barrel nut, have multiple receivers and check for best fit, or swap barrel nuts also looking for the best fit. My 11.5 SBR has one of these slightly over torqued barrel nuts and I beat on it like it owes me money. I’ll likely have the barrel shot out by the end of this summer, can more or less guarantee the receiver will be fine when I rebarrel. |
Joined:
Mar 2026
Posts:
21
EE: 100% (1)
OH, USA
|
Originally Posted By M4BlackRifle: A dab of AreoShell on the threads is recommended, but any good quality hi-temp grease or anti-seize is a reasonable substitute. … This. Regular antiseize, copper antiseize, brake caliper lube, Molykote, lithium grease, whatever. Loctite bearing retaining compounds can be used to fill and secure the barrel extension into the receiver - effectively bedding them together. There are various loctite retaining compound that offer a mix of strength vs temperature depending on the size of the gap to be glued; everything from tight interference shrink fits to “she’s finally to settle down”... Popular ones are 609, 648, 620, 680, and 660. 609 and 680 are my go to because you can buy the little eye-dropper amount for cheap from McMaster and not have a lifetime-supply bottle left over. 609 is good on tight shrink and 680 is good for both shrink and even loose fits. |
| The reciever is aluminum and barrel extension and lock nut are normally steel. Without an anti corrosive grease you can get galling due to dissimilar metals touching. So I would put grease on the threads and the barrel extension. Slide it into the reciever wipe off excess. Pretty much any grease will work. Aeroshell is the go to grease and a small tub will last you forever. |
|
Originally Posted By m4nut: May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! Tighten and loosen 3 times to stretch the threads then anywhere between 35-80ft/lbs to get the alignment right. This is pretty common it will never line up at a specific torque spec. It's a torque range because of machining specs no two recievers or barrel extensions are the same. |
Joined:
Sep 2022
Posts:
201
EE: 0% (0)
TX, USA
|
I use white lithium grease for anything that needs grease: trigger, buffer spring, threads on barrel nut. According to Ripcord industries installation instructions, you tighten it to torque once, then back it off, and then tighten it back to torque one final time. |
|
Originally Posted By m4nut: May I jump on this thread with a related question? Building an 11.5. Barrel installed in a BCM flattop upper. Threads heated to drop the 11.5 barrel into the front end of the BCM upper. Barrel seated flush and even. When I tighten down the barrel nut, I cannot get the proper alignment of the nut with the hole for the gas tube. The only was to achieve proper alignment is to: Leave the barrel nut looser than I would like...[not an option] Go beyond the 40FP recommended torque, and overtighten the damn nut....it'd be waaaaay too much. [again, not an option] I've prolly done a dozen or so builds over the years, never experienced this issue before. Are barrel shims the answer to my lament? Any help REALLY appreciated! |
"Major, with the weapon shops out of the way we can introduce steadying laws that could not be flouted." -A.E. Van Vogt 1951
|
Originally Posted By j3_: I have never understood how anyone even knows what torque is/needs to be applied to a thermal fit barrel and upper since you don't know how much torque it will take just to overcome the thermal fit before it begins to tighten the parts together. |
"Major, with the weapon shops out of the way we can introduce steadying laws that could not be flouted." -A.E. Van Vogt 1951
|
I normally use bcm thermal fit so no need for bedding, even without thermal fit its arguable whether or not you'll ever notice a difference bedding with loctite. I use aeroshell on the threads, extension ill just put a little G96 just to help lubricate for the thermal fit. So tad bit of oil on the extension, grease the threads. |
|
Originally Posted By j3_: I have never understood how anyone even knows what torque is/needs to be applied to a thermal fit barrel and upper since you don't know how much torque it will take just to overcome the thermal fit before it begins to tighten the parts together. ? When I put uppers together with thermal fit the index pin is bottomed out in the slot when I put them together. Before I start tightening the barrel nut. When the upper is warm it'll accept the extension until its all the way in. A little tap with a dead blow hammer immediately after slipping it on ensures you are indeed bottomed out. |
|
Originally Posted By FoxValleyTacDriver: ? When I put uppers together with thermal fit the index pin is bottomed out in the slot when I put them together. Before I start tightening the barrel nut. When the upper is warm it'll accept the extension until its all the way in. A little tap with a dead blow hammer immediately after slipping it on ensures you are indeed bottomed out. Originally Posted By FoxValleyTacDriver: ? When I put uppers together with thermal fit the index pin is bottomed out in the slot when I put them together. Before I start tightening the barrel nut. When the upper is warm it'll accept the extension until its all the way in. A little tap with a dead blow hammer immediately after slipping it on ensures you are indeed bottomed out. There is supposed to be at least a .003" or larger gap between the back of the slot and the index pin by design. The extension should seat on the face of the upper. So you tighten the nut with the aluminum threads expanded from the heating? I got this when I searched the question of the two forces one the thermal fit and the other opposing outside force. I don't see how you have any idea of what force a torque wrench reading on a barrel nut means if you don't know both. Just a question I wondered about on the thermal fit thing. In short: Clamping force is internal and doesn’t directly cause motion. Outside force is external and can cause motion if it exceeds the resisting forces. Lowering the clamping force below the outside force means the outside force will dominate, and the objects will move in its direction. |
|
Again, thanks for all the help. On the 5th tightened/loosened/tightened, all aligned.Attached File Attached File |
...Amongst the 1911 poors...
|
Originally Posted By m4nut: Again, thanks for all the help. On the 5th tightened/loosened/tightened, all aligned.https://www.ar15.com/media/mediaFiles/20054/1000027831_jpg-3742153.JPGhttps://www.ar15.com/media/mediaFiles/20054/1000027831_jpg-3742154.JPG Some threads need a bit more "seasoning" than others. Glad to see that you got it together. |
|
Originally Posted By DancingInAshes: I use white lithium grease for anything that needs grease: trigger, buffer spring, threads on barrel nut. According to Ripcord industries installation instructions, you tighten it to torque once, then back it off, and then tighten it back to torque one final time. |
Joined:
Sep 2022
Posts:
202
EE: 0% (0)
TX, USA
|
Originally Posted By MaxSpeed74: Once you get a thermal fit barrel in to where you can engage the threads you can generally tighten it to contact with your fingers so... 5 ft/lbs max? Pretty much. When I installed my criterion core on my BCM stripped upper, I was able to get it almost all the way in just by pushing and wiggling. Then I put the barrel nut on and GENTLY tightened in to push the barrel all the way in. Then I took the barrel nut off, used a bit of white lithium, and torqued it to spec once, backed it off, and torqued it to spec a second time for final installation. |
Joined:
Sep 2022
Posts:
203
EE: 0% (0)
TX, USA
|
Originally Posted By Blowout: I've used Lucas white lithium grease on several barrel nuts, buffer springs and such over the years. it seems to dry up and get chunky after several years so I switched to aeroshell. The lithium grease I have seems to separate out the oils from solids over time. I haven't noticed this happening at all with Aeroshell. That's an interesting point you make there. Just from reading this thread I think I'll switch to aeroshell for future builds or modifications. |
AR Sponsor