Torque Wrench

[Knuckle Dragger]

How important is it to use a toque wrench when installing an AR barrel?

 

[SJan]

Not needed
It is almost always necessary to go over the recommended torque value to line up the gas tube anyway.
Do you have a vice block and barrel wrench?
Use some moly grease on the threads, tighten it in all the way, back it out, send it in again until its tight, then go a bit more to line up the gas tube.

I had to google the torque value, and this is what I remember reading a while back

Tighten the barrel nut to 35 ft lbs, then loosen and tighten twice more. On the third time after you have mated the receiver threads to the barrel nut, hit the 35 ft lbs, then without going over 80 ft lbs, tighten the nut past the 35Ft lbs to index the top two nut spines to allow the gas tube to pass through them without binding.

 

[noddaduma]

Tag for future reference

 

[turbo89]

Not needed
It is almost always necessary to go over the recommended torque value to line up the gas tube anyway.
Do you have a vice block and barrel wrench?
Use some moly grease on the threads, tighten it in all the way, back it out, send it in again until its tight, then go a bit more to line up the gas tube.

I had to google the torque value, and this is what I remember reading a while back

X2! I torqued my most recent build and it seemed loose still (it was lubed properly). I went ~ 2 additional gas tube holes until it felt "snug", and all is well.

 

[Golddiggie]

I used a little white lithium grease on the threads for my barrel nut on the 300 Blackout build. Didn't use my torque wrench, just went to what I had read (tight then to the next proper hole alignment). Some freefloat hand guards don't have the gas tube pass through the nut. Those you should probably torque to the numbers to be sure it's good to go.

Isn't building/assembling your own AR fun??

Oh, if you're looking for a really good AR15/AR10 wrench, Fourrunner makes one. He has an ongoing 'group buy' for a couple versions. If you ever plan on making/owning an AR10 as well, get the one he makes that does both. The thing is a BEAST.

 

[Squire]

Make sure your vice is well mounted to your bench, 80lbs (measured or not) can rip the screws out of plywood pretty easily. I use the torque wrench primarily to make it easier to inspect gas tube hole alignment while applying torque (my wrench adds an extra 18" or so to my AR wrench). As Archimedes said, "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.".

 

[Golddiggie]

I'll use my 18" breaker bar next time I'm securing a barrel nut to an upper...

 

[ntomsw]

Use Aeroshell 33MS grease if you can find it on the barrel nut threads.

 

[Knuckle Dragger]

Not needed
It is almost always necessary to go over the recommended torque value to line up the gas tube anyway.
Do you have a vice block and barrel wrench?
Use some moly grease on the threads, tighten it in all the way, back it out, send it in again until its tight, then go a bit more to line up the gas tube.

I had to google the torque value, and this is what I remember reading a while back

Thanks for all the responses. I do have a vice block and barrel wrench. I'm just not sure if I still have a torque wrench.

 

[Rob Boudrie]

It is almost always necessary to go over the recommended torque value to line up the gas tube anyway.

I believe the recommend range is 30-80 ft lbs. Are you saying you have to go over 80 to line up the tube?

 

[SJan]

I believe the recommend range is 30-80 ft lbs. Are you saying you have to go over 80 to line up the tube?

Many searches show 35lbs barrel nut torque without describing the method.
(I meant it is necessary to go over this value)

If actually using a torque wrench the proper method would be something like this:
Torque to 30lbs, fully loosen.
Torque to 30lbs, fully loosen again.
Torque to minimum 35lbs, if gas tube does not line up, continue without exceeding 80lbs until gas tube lines up.

35-80lbs is a very broad range. The anodizing in the upper receiver, the phosphate of the barrel nut, the type and amount of grease used on the threads (or lack of! ) will all vary the degrees of rotation of the nut between 35-80lbs.

 

[GunGrey]

I used one just because i had it sitting around. Did i need it? nope could have done it without it.

took me 15 mins to assemble the upper and that was with a beer run to the fridge

 

[Canndo]

Many searches show 35lbs barrel nut torque without describing the method.
(I meant it is necessary to go over this value)

If actually using a torque wrench the proper method would be something like this:
Torque to 30lbs, fully loosen.
Torque to 30lbs, fully loosen again.
Torque to minimum 35lbs, if gas tube does not line up, continue without exceeding 80lbs until gas tube lines up.

35-80lbs is a very broad range. The anodizing in the upper receiver, the phosphate of the barrel nut, the type and amount of grease used on the threads (or lack of! ) will all vary the degrees of rotation of the nut between 35-80lbs.

Agreed. I've done multiple builds without grease or a torque wrench and never had a problem. The last build, a .308 LR, I figured I'd throw some grease on and torque it to specs. This thing went from -30lbs to well over 100lbs between notches. I chalked it up to excess grease but man that one was a bitch.

 

[Gammon]

A torque wrench is not necessary as the specs are very broad and the final torque is controlled by the relationship between the barrel nut and the gas tube. A lubricant helps as it eliminates friction so you can feel exactly what you are doing. I prefer "anti seize" compound because it will not cook off like conventional grease and will help in disassembly.

 

[jd4444]

When using a torque wrench if you lubricate the threads (reduce friction) you will actually be applying more torque than you wish to. Just like if you add a friction modifier like locktite (add friction), you will actually torquing it to less than you want to. If you are using a dogbone attachment it should be orientated 90 degrees from the wrench, if it is more or less than 90 degrees there is a formula you need to use.

When given a torque range and you need something to line up within that range, like a cotter pin and a castellated nut, you go to minimum torque and see if everything lines up. If it does not line up, adjust the wrench to max torque and see if everything lines up before the wrench clicks.

 

[jakeroub]

I you are interested in using a torque wrench (and you care to be accurate) you should have the torque wrench handle at a 90 degree angle from the centerline of barrel nut wrench. If you have the torque wrench lined up with the nut wrench, you will be adding distance to your lever arm and applying a higher torque than the wrench is showing. For example, if you have a 24" long torque wrench handle and you add 3" to the lever arm, a 80 ft-lb reading will actually apply 89 ft-lbs to the nut. Maybe not important in this application, but worth remembering anytime you are torquing something with a special tool like this.

 

[Sir_Gawain]

I did mine according to Larry Potterfield