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Do I really need to use a torque wrench when tightening the barrel nut on my AR upper? Or is it fine to just tighten it to the point at which the gas tube lines up properly?
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Barrel Nut / Torque Wrench
- Thread starter BullieBred
- Start date
It is a wide range so it depends on how good you are at estimating. I used a cheap-o old Craftsman beam torque wrench. When in doubt back it off and do it again.
Want to do some home engineering: hang a weight off the end to the wrench and calculate the torque applied. I did this to check my cheap-o Craftsman torque beam wrench before use and it worked well. Tricky part is the measurement is only valid when the nut is moving![[thinking]](/xen/styles/default/xenforo/smilies.vb/010.gif "Thinking [thinking]")
Next question: what type of grease to put on the nut?
Answer: TW25B is good; any graphite free grease or oil is better than nothing
EDIT: there it is http://www.northeastshooters.com/vbulletin/threads/109141-How-tight-is-35-ft-pounds-of-torque
Want to do some home engineering: hang a weight off the end to the wrench and calculate the torque applied. I did this to check my cheap-o Craftsman torque beam wrench before use and it worked well. Tricky part is the measurement is only valid when the nut is moving
Next question: what type of grease to put on the nut?
Answer: TW25B is good; any graphite free grease or oil is better than nothing
EDIT: there it is http://www.northeastshooters.com/vbulletin/threads/109141-How-tight-is-35-ft-pounds-of-torque
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You don't really need a torque wrench. I believe the spec is 30 to 80 foot pounds so you don't have to be very precise. The alignment of the holes in the nut and upper for the gas tube is really the determining factor. I did my most recent upper with a strap wrench I bought at Lowes for about $10.00.
The grease is critical, however. You need a high temp anti seize compound that won't bake on or you will have a terrible time trying to disassemble the upper at a later date. This stuff is available at any auto parts store.
The grease is critical, however. You need a high temp anti seize compound that won't bake on or you will have a terrible time trying to disassemble the upper at a later date. This stuff is available at any auto parts store.
KMM696
NES Member
Go ahead - what's the worst that could happen.
I'm sure there have been many ARs that have had a barrel successfully installed without benefit of torque wrench. It's not a real tight torque spec to hit, after all. (Tighten to 30 ft-lbs and loosen 3 times, tighten to 30 and then continue tightening until the gas tube lines up. Do not tighten past 80 Ft-lbs.) If your calibrated elbow can torque between 30 and 80, it should be fine.
The barrel nut and upper receiver aren't responsible for restraining the pressures generated by firing, but they are responsible for aligning the parts that do. While it is probably very unlikely that a catastrophic failure due to not torquing will occur, that risk can be effectively minimized by using a torque wrench.
My risk analysis leads me to using torque wrenches - all the time. Your analysis may be different - after all, risk can be minimized to acceptable levels, but not eliminated. Good luck.
I'm sure there have been many ARs that have had a barrel successfully installed without benefit of torque wrench. It's not a real tight torque spec to hit, after all. (Tighten to 30 ft-lbs and loosen 3 times, tighten to 30 and then continue tightening until the gas tube lines up. Do not tighten past 80 Ft-lbs.) If your calibrated elbow can torque between 30 and 80, it should be fine.
The barrel nut and upper receiver aren't responsible for restraining the pressures generated by firing, but they are responsible for aligning the parts that do. While it is probably very unlikely that a catastrophic failure due to not torquing will occur, that risk can be effectively minimized by using a torque wrench.
My risk analysis leads me to using torque wrenches - all the time. Your analysis may be different - after all, risk can be minimized to acceptable levels, but not eliminated. Good luck.
everyone should own one whether it's for working on an AR or for working on anything else that requires something torqued to a particular specification.
Exactly. There's certain tools (and other things) every man should own.
Last year, during one of the big floods in MA, some marketing weasel at work sent out an email asking if he could borrow a shop vac because his basement was flooded. How can anyone who owns a house not own a shop vac? Similarly, how can anyone building an AR not own a torque wrench?
Anyway, the first person to reply saying he could borrow one was a gay guy, who owned two shop vacs. Hopefully this little story gets the point across.
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It's really not super critical. Most people seem to want to over-tighten them. Use some good moly grease, put the nut on so that it's snug, and then tighten to the next hole. You'll be fine.
SJan
NES Member
This. There is so much space between the holes for lining up the gas tube, that the torque value is moot.
Also: A torque wrench is made and calibrated to be used with a socket. When used on an AR15 armorer's wrench, the leverage is different, and the torque value will not be exactly what the wrench is set for.
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cmacclel
NES Member
You don't need a torque wrench on an AR Barrel. After the barrel nut gets snug and you have to put some effort in obtaining the first hole that lines up with the gas tube then your good. If you don't have to put any effort in to reach the first hole then you go to the 2nd hole and your done.
Mac
Mac
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There's a simple formula that corrects this. But a torque wrench and do it right. There are torque specs for a reason. I've seen two Differant home "builds" with hand tight barrel nuts mid match, they should have used torque specs and proper tools assembling there rifles.
You mean... some of you guys actually adhere to torque values?
As long as it's snugged down and tighter than a nuns twat... I'm good to go.
Pro Tip: Use an 11/64 or #16 drill bit to get the alignment dead on.
I know... they're not that common to find, but local Ace Hardware/Aubochon usually has off the wall stuff like that.
As long as it's snugged down and tighter than a nuns twat... I'm good to go.
Pro Tip: Use an 11/64 or #16 drill bit to get the alignment dead on.
I know... they're not that common to find, but local Ace Hardware/Aubochon usually has off the wall stuff like that.
you're fine. my poor rifle has been barreled and re-barreled so much and it never got grease because i was hating it in the face at the time i was doing all this. shoots fine now.
cmacclel
NES Member
Hmm which brand would this be? I have built a few AR's and cut down a bunch of barrels for people and have yet to come across a barrel nut without a gas tube hole.
Mac
cmacclel
NES Member
I use a torque wrench for everthing. For an AR you do not need one....unless you personally would like to know what your torque value was. Have you ever built an AR??
The paradox here is if you have a torque wrench you probably have enough experience to estimate the 30 to 80 lb spec and don't need to use it but if you haven't used one then you probably don't really know and now need to acquire one.
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You really should use a bit of moly grease. Aluminum recovers and steel barrels should have something between them to prevent seizing. Ever try to get an aluminum rim off of a steel hub after it's been on there a while?
While that's true, anodized aluminum doesn't have that problem. The anodized surface is quite immune to galling. Of course, if the anodizing gets scratched (which it will a bit during installation) that's different. I used anti seize.
There aren't many wheels that are anodized.
cmacclel
NES Member
Sorry but that statement is wrong
Dry anodized aluminum against dry anodized aluminum is the absolute worst when it comes to galling. I use to often have threaded things hard anodized and *once* made the mistake of "dry" fitting a pair. I had to soak the parts in oil in order to get them apart.Mac
Sorry but that statement is wrong
Mac
Fair enough, though I thought we were talking about anodized aluminum against steel.
cmacclel
NES Member
Most of the Barrel nuts I have used have been aluminum(YHM). I don't know the outcome on steel as I always put s very light coate of grease before assembly.
Mac
we are talking about aluminum on steel (OE style nut), and as far as using a torque wrench I think it is foolish not to use on on everything but this is just my opinion,
Bushmaster had this problem years back where the locator pins were bending throwing the barrel/sight alignment off from over torquing of the barrel, This came right from a bushmaster employee while I was there visiting the plant in windham years ago, besides why take the chance? 40Ftlbs to you may only feel like 10ftlbs to someone else! also we are talking about a fine thread aluminum with a fairly thin wall and a rather large nut, the last thing I would want to do is rip the threads off my upper or tighten it to the point it galls, don't be anxious and just do the right thing, they put a spec on it for a reason...
also the barrel nut threads Should be lubricated, the recommended lubricant suggested by Colt is Aeroshell 33MS, but I would think any medium bodied lube would be fine
