Should a barrel nut on an AR ever be re-tightened?

[paul73]

I have a head scratching moment here.
Other day while shooting a test, I had a feel examining the rifle that barrel may ( or may not) have too much of a free play inside the hand guard. It does not wobble free, of course, but held between index finger and thumb I could feel it moving up and down that felt as too easy - it should move but I am not sure of for how much. Now, when it is cold, I feel it moves less. It is a 20” heavy barrel, and I am not sure if it supposed to have that much flex.

Nut sits on red loctite most likely and not movable easy. I wonder if I lose my marbles here, or is it a possibility that after 1-2k shots there can be any play introduced in the barrel to upper joint that may warrant the removal and retightening of the barrel nut?
Or am I nuts and it never happens and some play on hot barrel after series of 200 shots is warranted?

 

[50wt]

Is this the same rifle that you've been chasing the perfect ammo recipe for ?

 

[paul73]

Is this the same rifle that you've been chasing the perfect ammo recipe for ?

Yep, so I may be seeing something that ain’t there.
Rifle was extremely reliable, but, I shoot it quite a lot.
Anything to say on the topic?

 

[moojpg2]

I have a head scratching moment here.
Other day while shooting a test, I had a feel examining the rifle that barrel may ( or may not) have too much of a free play inside the hand guard. It does not wobble free, of course, but held between index finger and thumb I could feel it moving up and down that felt as too easy - it should move but I am not sure of for how much. Now, when it is cold, I feel it moves less. It is a 20” heavy barrel, and I am not sure if it supposed to have that much flex.

Nut sits on red loctite most likely and not movable easy. I wonder if I lose my marbles here, or is it a possibility that after 1-2k shots there can be any play introduced in the barrel to upper joint that may warrant the removal and retightening of the barrel nut?
Or am I nuts and it never happens and some play on hot barrel after series of 200 shots is warranted?

you sure the handguard isn't flexing, not the barrel. I've never had one loosen up that was torqued properly, I usually put a swipe of high temp anti seize on mine actually, makes it easier to replace the barrel when the time comes. Red loctite has no place on anything gun related, especially a barrel nut. I would leave well enough alone. Red loctite has to be heated to 500 degrees for a while to be able to loosen it, royal pain in the ass.

 

[50wt]

Barrels will flex a bit, depending on the profile, but the barrel should not be loose.

 

[Rob Boudrie]

How could the barrel nut possible loosen? One of the notches has to be lined up with the gas tube that is installed after the barrel. The tube through this notch would prevent the barrel from loosening to any meaningful degree (probably just a fraction of a degree until blocked by the gas tube). The torque range is pretty wide - 30-80 ft lbs according to the Armalite instructor I took the class from.

 

[DrBurnsides]

I had a stag model 6 var inter with issues. It was a perfect tack driver for 1-2k rounds then not on paper at 100 yards. bolt was unevenly worn. I need to do a takedown. But either the receiver stretched or the nut came loose

 

[mothybee]

If the barrel keeps falling off I would.

 

[Mr. Brownstone]

How could the barrel nut possible loosen? One of the notches has to be lined up with the gas tube that is installed after the barrel. The tube through this notch would prevent the barrel from loosening to any meaningful degree (probably just a fraction of a degree until blocked by the gas tube). The torque range is pretty wide - 30-80 ft lbs according to the Armalite instructor I took the class from.

If its a free float barrel, there are no notches. But yeah, I’m with you, havent had one loosen on me yet.

 

[Mountain]

you sure the handguard isn't flexing, not the barrel. I've never had one loosen up that was torqued properly, I usually put a swipe of high temp anti seize on mine actually, makes it easier to replace the barrel when the time comes. Red loctite has no place on anything gun related, especially a barrel nut. I would leave well enough alone. Red loctite has to be heated to 500 degrees for a while to be able to loosen it, royal pain in the ass.

+1 for the anti-seize. I realize too late for OP, but getting it torqued down with anti-seize I've never had one come loose including 6.5 Creedmoor and .458 socom.

 

[paul73]

How could the barrel nut possible loosen? One of the notches has to be lined up with the gas tube that is installed after the barrel. The tube through this notch would prevent the barrel from loosening to any meaningful degree (probably just a fraction of a degree until blocked by the gas tube). The torque range is pretty wide - 30-80 ft lbs according to the Armalite instructor I took the class from.

I know, hardly possible.
Now when cold amount of flex of that 20” barrel is same or extremely close to other 3 ARs I got.

Barrel nut definitely did not move, it sits on loctite LaRue placed there, I could not make it bulge yesterday setting torque wrench to 80ft/lb, did not want to go higher.
Barrel nut LaRue uses is not locked by gas tube, it is round.

I just know the symptom of groups widening up with heat may be due to some excessive play in barrel/upper joint, but I am probably wrong, in this case.

If no one ever had to touch barrel nut once torqued - that is my answer… will keep looking at what else to do.

 

[50wt]

If its a free float barrel, there are no notches. But yeah, I’m with you, havent had one loosen on me yet.

Not necessarily. I have 3 handguards with 3 different barrel nuts. all free floating. A Troy uses the original notched style, a threaded handguard uses a threaded barrel nut that is drilled through, and a smooth barrel nut for clamp style.

 

[greencobra]

you sure the handguard isn't flexing, not the barrel. I've never had one loosen up that was torqued properly, I usually put a swipe of high temp anti seize on mine actually, makes it easier to replace the barrel when the time comes. Red loctite has no place on anything gun related, especially a barrel nut. I would leave well enough alone. Red loctite has to be heated to 500 degrees for a while to be able to loosen it, royal pain in the ass.

this^

and i dunno, red loctite has never touched any gun of mine...a friend told me to say that.

 

[paul73]

this^

and i dunno, red loctite has never touched any gun of mine...a friend told me to say that.

it is not me - larue does it. it is relatively well known - once they put it together, you cannot really pull gas block off, and undo the nut is also a trick. they do same on muzzle devices unless you specifically ask them not to - that i did.

 

[PappyM3]

it is not me - larue does it. it is relatively well known - once they put it together, you cannot really pull gas block off, and undo the nut is also a trick. they do same on muzzle devices unless you specifically ask them not to - that i did.

Red loctite on the gas block is common with manufacturers like BCM, but there should NOT be red loctite under the barrel nut. Just anti-seize/temp resistant grease. You can use green 609/620 loctite on the barrel extension, but not the barrel nut.

With a properly torqued barrel nut, it should not loosen or allow movement of the barrel at the nut. I’ve never seen it in any of my guns, nor in any of the ~200ish M4s/M16s in my Company’s arms room while I was the armorer for a few years and two deployments. Granted, it wouldn’t be as obvious with the toothed barrel nuts, but it wasn’t reported during level 20 maintenance.

But, that doesn’t mean you’re not experiencing it. A heavy profile barrel should not flex much at all. When checking for flex, you should not be holding the handguard, but rather have the upper clamped in a vice.

Without seeing the flex, it’s hard to say, but if it is moving at the barrel nut, I’d either contact Larue or just use a heat gun and breaker bar myself to remove the nut to check fitment and reassemble to my personal QA level.

 

[paul73]

should not be holding the handguard, but rather have the upper clamped in a vice.

That I can do.
Any idea how much flex in mm is allowed on a 20” heavy barrel? I can at least measure that.

 

[PappyM3]

That I can do.
Any idea how much flex in mm is allowed on a 20” heavy barrel? I can at least measure that.

I’m not sure about a quantified expected range, but later tonight I might be able to check my 20” service rifle target barrel and 20” SP1 pencil barrel with specific weights hanging off to see what kind of flex they show.

 

[Mountain]

I know, hardly possible.
Now when cold amount of flex of that 20” barrel is same or extremely close to other 3 ARs I got.

Barrel nut definitely did not move, it sits on loctite LaRue placed there, I could not make it bulge yesterday setting torque wrench to 80ft/lb, did not want to go higher.
Barrel nut LaRue uses is not locked by gas tube, it is round.

I just know the symptom of groups widening up with heat may be due to some excessive play in barrel/upper joint, but I am probably wrong, in this case.

If no one ever had to touch barrel nut once torqued - that is my answer… will keep looking at what else to do.

Possibly you have some play between the upper and lower receivers? Might make it feel like the free float is loose. For most purposes, that play is no big deal. For a match rifle or tightest groups exercise, you'll want to take up that play. Don't spend money on those rubber wedges etc. Get a few small no. 7 O-rings from the hardware store and slip one over the front trunnion on the upper receiver. Will be a tight fit so you might need a credit card or drivers license etc. to push all the way to bottom. Put upper and lower together via the front pin first, at an angle. Now close up the rear, squeeze it together and push the rear pin home. Slop is now gone.

 

[paul73]

Possibly you have some play between the upper and lower receivers? Might make it feel like the free float is loose. For most purposes, that play is no big deal. For a match rifle or tightest groups exercise, you'll want to take up that play. Don't spend money on those rubber wedges etc. Get a few small no. 7 O-rings from the hardware store and slip one over the front trunnion on the upper receiver. Will be a tight fit so you might need a credit card or drivers license etc. to push all the way to bottom. Put upper and lower together via the front pin first, at an angle. Now close up the rear, squeeze it together and push the rear pin home. Slop is now gone.

vertical play from upper/lower is generally mitigated by the adjustment bolt in the aero lower - it presses the rear takedown pin assembly up. rifle is reasonably tight, so, over the weekend i will probably break it all apart just for my mind sake to see what it is in there.

 

[milktree]

If its a free float barrel, there are no notches. But yeah, I’m with you, havent had one loosen on me yet.

Huh? How do you tighten the barrel nut without some sort of notch?

You still need a slot for the gas tube.

Can you post a picture of a notch-less barrel nut?

 

[Mr. Brownstone]

Huh? How do you tighten the barrel nut without some sort of notch?

You still need a slot for the gas tube.

Can you post a picture of a notch-less barrel nut?

 

[milktree]

View attachment 545704View attachment 545705

Huh!

Cool, thanks.

I hadn’t seen radial notches like that before.

My AR with a free float tube looks almost mil-spec.

 

[Mr. Brownstone]

Huh!

Cool, thanks.

I hadn’t seen radial notches like that before.

Midwest Industries. Not sure whst others do.
In my armorers course, they talked about stsndard barrel nuts, and under torquing in order to line up with gas tube being better than over torquing. On these, I go right to 40. No issues. But if there was wobble, id just retighten.

 

[Mountain]

vertical play from upper/lower is generally mitigated by the adjustment bolt in the aero lower - it presses the rear takedown pin assembly up. rifle is reasonably tight, so, over the weekend i will probably break it all apart just for my mind sake to see what it is in there.

Gotcha, yours has the bolt.

 

[1903Collector]

this^

and i dunno, red loctite has never touched any gun of mine...a friend told me to say that.

I have a JP hand guard and one gun and the install instructions specifically say to use red loc-tite (or equivalent) on the barrel nut.

 

[Rob Boudrie]

I have a JP hand guard and one gun and the install instructions specifically say to use red loc-tite (or equivalent) on the barrel nut.

Is this is reference to the big thread of the barrel nut, or of the threaded connectors the JP handguard uses to attach to the barrel nut?

 

[ThePreBanMan]

Tighten it up every time you change the oil..

 

[PappyM3]

Midwest Industries. Not sure whst others do.
In my armorers course, they talked about stsndard barrel nuts, and under torquing in order to line up with gas tube being better than over torquing. On these, I go right to 40. No issues. But if there was wobble, id just retighten.

The vast majority of free float handguard barrel nuts don’t have teeth that would require timing with the gas tube.

 

[Mr. Brownstone]

The vast majority of free float handguard barrel nuts don’t have teeth that would require timing with the gas tube.

Didnt think so. All mine are midwest,

 

[paul73]

I have a JP hand guard and one gun and the install instructions specifically say to use red loc-tite (or equivalent) on the barrel nut.

Red loctite is a solution for sell it and forget it model. To take anything apart that was on red is a huge pita. Especially a nut that was torqued to 80 ft/lb.