Technically in the mechanic world, torquing with an adapter attached to the torque wrench you're supposed to keep the wrench at a 90 degree angle.

I haven't really seen anyone care about this when torquing with armorer's wrenches.... they seem to just go straight inline with both wrenches.  Isn't this wrong?

Mechanically, you are correct.  The torque "seen" at the wrench will be different than seen at the barrel nut due to the adapter offset.



However, the common thought is since you're dealing with a huge window of torque values (35-80 foot pounds), exact precision in this isn't worth the headache trying to calculate the variation due to the adapter. Just get it somewhere in there, and timed if needed for that type of nut.

I go to my planned torque and add 10% to the calculation.

Or on a lazy day 45ft-lbs.

So is it ok if I torque with my wrench at 90 degrees if I wanted to be 100% accurate?  

I just watched a video where this dude said the Army TM manual says to torque with the wrench inline with the armorer's wrench and that torquing at 90 degrees is wrong

well if the Army says it......

Here's an easy online calculator
http://www.cncexpo.com/TorqueAdapter.aspx

The torque spec in the Army TM is with the armorer's wrench IN LINE with the torque wrench.  The TM doesn't care what the "actual" torque applied to the nut is, only that you get at least 30 foot pounds and not more than 80 foot pounds "indiated" on your wrench.

If you do the math, the difference between the TM method, "the right way", and the actual torque applied to the nut is only a few percent.  But I follow the TM procedure because that's what the gun is designed for.

If the TM states to use the tool inline with the Tq wrench, the calculations have already been adjusted for the end user.  For instance, some engineer calculated the proper torque range to be 34 to 85 foot lbs.  By telling you to use the tool inline, and setting the wrench from 30 to 80 foot pounds, they have accounted for the difference and provided the adjusted instructions you should follow.  My numbers are made up, but you get the idea.

In mechanic terms, when they say extending the Tq wrench changes the value, that is for cases where you may not have control of the socket, dog bone, crow's foot, etc that you have to use.  Stated torque values are normally applied at the head of the wrench.  If you are forced to use a crow's foot or dog bone, you have to place it at 90 degrees to achieve the same tq value.  In that case, you are being accurate.  In the case of the armorer's wrench, you are just deviating from instructions.

Just get it tight.

Doesn't the whole 90 degree thing have to do with the APPLIED FORCE on the moment arm, and not the arrangement between the tq wrench and the adapter?

AFAIK the moment arm of the adapter will cause the actual torque to be slightly higher than when the wrench clicks, but not much more. Right?

I am not understanding your question or point.  We all know that the orientation or arrangement of the tool in relation to the center point of the tq head affects the torque reading.  Whether that is changing the moment, or the applied force, or whatever.   If the arrangement lengthens or shortens the distance from the handle to the tq head, you will get a different tq than what you set.   If the arrangement is 90 degrees, the difference is negated, and you will get the actual tq to which you have set the dial.  That is changing the arrangement between the tq wrench and the adapter, or the tool, so there is a direct correlation.  Why would you claim the 90 degree thing has nothing to do with the arrangement between the two?

Jesus man. A simple "no, that's not correct" would have sufficed, LOL.

Follow directions.  That's always a good idea.

If the Army TM says attach the adaper to the torque wrench parallel (straight ahead)(and it does), that's what they have already done in determining the recommended torque.  Don't try to do the math.  Just follow instructions.

Same thing with aftermarket barrel nuts that are not milspec.  Follow instructions.  They will tell you whether to install the adapter straight or at 90 degrees.  Only if they were silent would I assume that I would have to use 90 degrees to keep the leverage arc as close as possible.

Good things generally happen when you follow instructions.

I just looked for where is says to use the torque wrench and the barrel wrench "IN LINE" and I couldn't find it.

An image is shown with the torque wrench and barrel wrench "IN LINE" but based on how inaccurate all of the other images in the TM are I would take it with a heavy dose of salt.

However, I do use my torque wrench, barrel wrench and stock wrench "IN LINE" with each other.

The value given in the TM is corrected for the offset from the USGI wrench adapter.

The difference between the USGI adapter and a commercial adapter is nothing....

Precisely.

Type of lubrication also affects the calculation, and is probably a bigger deal than a small difference in the moment arm. You definitely want to be in the same ballpark friction coefficient as the specified lube. Tightening the barrel nut dry, for an extreme example, will give you much less clamping force for a given torque value exerted on the wrench.

But people often get anal about this. Unless you're going for crazy accuracy, your sweet spot is tight enough that the barrel doesn't wobble in the receiver, not so tight that you compromise the threads. You really have a pretty big window. That said, if I were re-designing the AR 15, I'd come up with a barrel nut and handguard retention mechanism that didn't need to be timed.

Whether or not there is grease on the threads makes a big difference, type of grease, not so much....

No timing?  Like an AR10?