Gunsmithing AR Barrel Nut with a strap wrench question..

[rawdeal77]

I'm installing a WOA FFT tube, and the barrel nut is installed with a strap wrench.

Using a strap wrench to tourque on the barrel nut, how do you know when it's tourqed properly?

Do they make a strap wrench with a socket hole in the base where you can supplement a tourque wrench?

If I were using socket wrench, I would know where my 40-80 ft/lb range was on feel, but I don't know if I trust my feelers with with strap wrench just bec. the hanlde is so much shorter than what I'm use to.

 

[jacq220]

Re: AR Barrel Nut with a strap wrench question..

tighten it down until its snug, then go to the next gas tube hole. you might have to torque then loosen a few times to get it to tighten up enough to line up on the next gas tube hole correctly.

 

[gunnergirl81]

Re: AR Barrel Nut with a strap wrench question..

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JACQ</div><div class="ubbcode-body">tighten it down until its snug, then go to the next gas tube hole. you might have to torque then loosen a few times to get it to tighten up enough to line up on the next gas tube hole correctly. </div></div>

+1. The nature of the barrel nut on the AR/M16 platform doens't lend itself to being able to be set to a specific torque. More like a min. torque standard. You have to just be sure its tight enough to prevent the barrel extension from being able to wiggle, and that the gas tube holes align.

 

[KTDLS7]

Re: AR Barrel Nut with a strap wrench question..

Minimum torque spec for an AR15 barrel nut is 35 LB/ft (which is more than "snug"), then continue tightening to the next gas tube hole. If you have an in-line (HD fish/game) scale, do a quick calculation on the length of the strap wrench handle and pull accordingly to attain the 35 LB/ft minimum.

Kevin

 

[rawdeal77]

Re: AR Barrel Nut with a strap wrench question..

I should add, there are no gas tube holes to deal with here. The outside diameter of the barrel nut is small enough as not to interfear with the gas tube.

The game scale suggestion should work though. What is the formula for the calculation?

Let's say it's a 10" handle.

 

[RADcustom]

Re: AR Barrel Nut with a strap wrench question..

Don't over think it. It isn't rocket science.

There is a wide range torque spec in order to line up the holes. Since you don't have that to contend with, just tighten to the point that you feel comfortable that the barrel nut will not shoot loose.

 

[KTDLS7]

Re: AR Barrel Nut with a strap wrench question..

As RADcustom stated, it's not "rocket science", but the barrel nut has to be tight - you don't want it shooting loose.

Regarding specs, the last AR15/M16 armorer course I atteneded (2010) stated "minimum 35 LB/ft". The military docs state 31 min, not to exceed 80 LB/ft. Military procedure is tighten to 30 LB/ft and loosen three times, then final tighten to 31 and continue until gas tube is aligned.

To answer your question above regarding calculation:
(12/x)*torque LB/ft, where x=length of arm in inches
In your case, (12/10)*35=42 You would pull on the game scale 42LBS perpindicular to the arm.
I have used this when tightening a fastener and could not use a torque wrench due to confined spaces.

Kevin

 

[rawdeal77]

Re: AR Barrel Nut with a strap wrench question..

Great advice, guys. THnaks for the help.

 

[Beef_Supreme]

Re: AR Barrel Nut with a strap wrench question..

Not to throw a strap wrench in your gearbox, but what caliber AR are you building? Different calibers require different minimum torque requirements.