Ar15 Barrel Nut

[outerlimits]

happened to notice a very, very slight movement in my upper...if i grab the free-float tube and turn it, there's a tiny bit of movement-very tiny. i assume it's the barrel nut, but i'm not sure. if it is the nut, what does such small movement mean to accuracy?

[Wakal]

Is it the barrel nut threading onto the receiver or the handguard threading onto the barrel nut?

Colt thinks that 35 foot-pounds is optimal for a barrel nut. Around here, we run them to hand tight (no straining or cheater bars on the wrench ) and then set up the gas tube on the "next" hole in the barrel nut. Don't forget the anti-seize on the receiver threads

Alex

[George]

what does such small movement mean to accuracy

Nothing good if the bbl is loose too ;-/

If it's the bbl nut itself thats loose and you don't have the bbl vice and bbl nut wrench needed here, take it to a smith and have it fixed. There should be no movement in these parts at all unless it's just the handguard that's loose. The handguard threads on afterwards to either a threaded bbl nut, or whats left of the receiver threads after the bbl nut is on. In either case if it's just the handguard thats loose a tiny bit of blue loctite will do the job best. Re-torquing the handguard without the right tools can tweak things badly on some setups.

[outerlimits]

Is it the barrel nut threading onto the receiver or the handguard threading onto the barrel nut?

Colt thinks that 35 foot-pounds is optimal for a barrel nut. Around here, we run them to hand tight (no straining or cheater bars on the wrench ) and then set up the gas tube on the "next" hole in the barrel nut. Don't forget the anti-seize on the receiver threads

Alex

wish i could tell-i'm not really sure. the tube rotates a scane fraction of a degree, but looking at the inside barrel extension doesn't show any movement. the movement itself is subtle, and comes to a complete and tight stop-in other words, tiny movement to one direction, a hard stop, and tiny movement back to the other direction. i have a clark carbon fibre hanguard so i can't really see the barrel nut.

[Larry White]

Butch, your nut is loose and your groups open up. My Clark tube has backed off twice. Hard to get it tight again because the holes for the gas tube have to line up(the gas tube is what is keeping it from unscrewing now). Pull the gas manifold and tube, then unscrew the hand guard, Clean everthing up good, use a good size drop of blue loctite and reinstall, tighten to the point the gas tube will go thur the handguard and the reciever. Mine has stayed put for about 2k this time.------Larry

[George]

The reason there is only a tiny bit of movement before it stops is the gas tube goes through a hole in the handguard and you are hitting it each way you turn. Take it to a smith who knows AR's and have them replace the gas tube while they are at it if it's got high mileage on it. Larry has it right about loctite (blue only) if there are any lineup issues that prevent full torque being applied to the nut and/or handguard.

[Larry White]

2nd post, your going to need a reciever clamp or a big padded vise and a strap wrench. Put masking tape over the carbon tube to protect it and make the wrench bite better. Hard to get it tite and line up the holes, I cheated last time and got a little extra with a rat tail file.------Larry

[wsimpso1]

George is right on the money. Take it to a 'smith that understands AR's. I too use Loctite, and it works great. It may take heat to disassemble, but that is better than having it come apart when you do not want it to come apart.

Billski

[Patrick Sweeney]

A slightly loose barrel nut could have a bad effect on accuracy. And it might not mean anything. The only way to know is to test. However, if you're getting good groups now, you may just forego the whole testing routine.

As for loctite on the barrel nut, I never use it. I've not had a barrel ever come loose. However, I don't believe the B-S from Colt about 35 ft-lbs being enough. And based on a whole lot of Colt barrel take-offs, Colt doesn't either. I've taken M-16 barrels off where I could spin the barrel nut off by hand. I've also run into barrels where I had to machine the nut off to get the damn thing apart. (When the torque wrench reads over 100 ft-lbs, and the nut hasn't moved, I stop struggling and go to the mill.)

[anachronism]

Another thought... You could be feeling a slight amount of play between the recievers. I notice a slight amount of play between the recievers on my ARs. It is ever so slight, that I don't feel it's even worth an accu-wedge, or similar "fixes".