ar15 barrel nut tightness

[jvh22a]

this is my first ar15 assembly and i got the nut on and did the tighten/loosen about 10 times aready. the fingers on the nut will always end right at the openning for the gas tube. at 50lbft the finger will be in the way as i tighten to max 80 it will almost clear. just a bit more.

in your opinion should i just tighten it down just a bit more? cause if i loosen the nut it i would be in the 30lbft range. and that is just a bit tighter then hand tight.

compensator is already welded on and gas block in place so dont want to remove those.

[Arisaka]

That's what I did. works fine.

[wash]

You could remove the offending tooth.

[ColdDeadHands1]

I recommend putting a liberal amount of oil on the threads and do the tighten / loosen thing more until you get it to the tighter spot. I would not cut off the tooth.

[kcstott]

My USMC manual says tighten to 35 ft lbs, check alignment and tighten to next hole if needed for proper clearance of gas tube.

[bohoki]

you can file a bit off the front of the upper just enough to take the finish off it also helps with the retaining pin wear on the buffer sometimes

also use anti sieze paste on the threads

[phrogg111]

Whoa, you're torquing this nut 50 to 80 foot pounds? That's WAY too much!

Top end torque should never be above 40 foot pounds, and the range is more like 23-40 ft-lbs that you should be torqing it to!

Really, I've seen people using their AR-15s with the barrel nut torqued hand tight. If you're going up to 80 foot pounds, you're destroying the threads on your ALUMINUM upper receiver!

[jvh22a]

For the openning to line up the torque is only 10lbft, little less then hand tight. 40lbft the finger is right in front of the openning. So to get it to the next openning the torq will be near/pass 100lbft.

For those that filed fit, does the gas tube help with lining up the bcg?

[crazychinaman]

this is my first ar15 assembly and i got the nut on and did the tighten/loosen about 10 times aready. the fingers on the nut will always end right at the openning for the gas tube. at 50lbft the finger will be in the way as i tighten to max 80 it will almost clear. just a bit more.

in your opinion should i just tighten it down just a bit more? cause if i loosen the nut it i would be in the 30lbft range. and that is just a bit tighter then hand tight.

compensator is already welded on and gas block in place so dont want to remove those.

I would tighten a hair more .That would be ok.Did you forget to use never-sieze on the threads.?The stuff you put on brake pad calipers bolts.

[crazychinaman]

this is my first ar15 assembly and i got the nut on and did the tighten/loosen about 10 times aready. the fingers on the nut will always end right at the openning for the gas tube. at 50lbft the finger will be in the way as i tighten to max 80 it will almost clear. just a bit more.

in your opinion should i just tighten it down just a bit more? cause if i loosen the nut it i would be in the 30lbft range. and that is just a bit tighter then hand tight.

compensator is already welded on and gas block in place so dont want to remove those.

I would tighten a hair more .That would be ok.Did you forget to use never-sieze on the threads.?The stuff you put on brake pad calipers bolts.

[crazychinaman]

this is my first ar15 assembly and i got the nut on and did the tighten/loosen about 10 times aready. the fingers on the nut will always end right at the openning for the gas tube. at 50lbft the finger will be in the way as i tighten to max 80 it will almost clear. just a bit more.

in your opinion should i just tighten it down just a bit more? cause if i loosen the nut it i would be in the 30lbft range. and that is just a bit tighter then hand tight.

compensator is already welded on and gas block in place so dont want to remove those.

I would tighten a hair more .That would be ok.Did you forget to use never-sieze on the threads.?The stuff you put on brake pad calipers bolts.

[jvh22a]

Thanks for all the help guys. I ended up about 94lbft and the gas tube lined up perfect. If I backed it off to the openning before, it would have only been about 15lbft.


List of parts used:
-Upper
PSA blem and all the other stuff on it like dust cover.
Bcm gas block
Rainier select barrel
Rainier xtc
Rainier evo 11 rail
Magul mbus
Fail zero bcg and hammer
Bcm mod4 charge handle

-lower
Aero precision lower
PSA lower parts kit
Mega arms trigger
Magpul Moe+ grip
Magpul str stock

Here some pics.








Going to try it out on Thursday at Angeles.


*** last question. Headpace was checked before I took the barrel nut off. Since I reinstalled everything and the torque was about the same as before should I be ok? I only checked with a "no go gauge". All parts are new, if that matters.

[A.M.]

94 ft/lbs?

Dude-- that is more than what my RIM needs to stay on the car. It's supposed to be 30-40 ft/lbs, IIRC.

[wash]

Barrel nut torque does not change headspace. If you were ok before, you are ok now.

[Grumpyoldretiredcop]

Top end torque should never be above 40 foot pounds, and the range is more like 23-40 ft-lbs that you should be torqing it to!

Really, I've seen people using their AR-15s with the barrel nut torqued hand tight. If you're going up to 80 foot pounds, you're destroying the threads on your ALUMINUM upper receiver!

Not terribly good advice, phrogg. Whose specs are you referring to?

Barrel nut torque is 30-80 ft-lbs. or 35-80 ft-lbs., depending on whose manual you're using. While there's no way that the threads will be damaged using up to 80 ft-lbs of torque, 94 is a bit high Had the OP's barrel not already had the brake blind pinned in place, using some shims would have gotten that barrel nut into alignment without exceeding that upper torque limit. Unfortunately, that would require removing the barrel nut to install the shims... a little difficult in this case considering the already welded muzzle device.