I'm ready to torque down the barrel nut and noticed that the Daniel defense wrench requires a 1/2 wrench and I only have a 3/8. Will it hurt anything to use an adapter? I like the torque range better on the 3/8 wrench, I would rather not have to buy another torque wrench.

They do affect torque but its a very small amount. Just make sure you account for the extra length from the torque wrench head to the barrel nut. That will affect torque.

Addition of an adapter isn't going to make much difference, the minimum value is 30 foot pounds. That is an indicated value for the same reason the adapter changes it = the torque wrench is already at the end of the barrel nut adapter, not turning on the direct axis of the barrel bore line.

So it's already adapted numbering in the first place. Just a number already calculated with the extra bits hanging off the wrench.

As for the torque wrench, it's necessary to keep from exceeding 85 foot pounds as the worst case situation is the threads on the nose would start stripping out beyond that. 85 is a maximum, NOT an goal to achieve. if it can be done at a lower value, stop and it's done. If the wrench keeps hitting the max without lining a tooth up to pass the gas tube - the entire point of the exercise - then it's time to either use a shim or lap the nose.

These procedures were written by depot level supervisors to keep the average 20 something armorer in a unit from screwing up gov't property, using a kit developed to  service all the unit's weapons. The average mechanic with any experience level would know what 85 pounds feels like from a 12-16 inch lever, it's lug nut tight - and that's the maximum.

Some of us don't even bother with a torque wrench, we just tighten it up within reason to get the sprockets out of the way and move on. The range of acceptable torque is anywhere from 30 to 85 foot pounds, this is far from a precise procedure.

Alright if it's only a small difference I'll use an adapter and try to locate the formulas to calculate the difference. I know there's a wide torque range and its probably not as big of a deal as I'm making it out to be. Thank guys.

I don't use an adapter. The 1/2" torque wrench at Harbor Freight is $22 and "coupons" can be found on the Internet that let you buy for $9.99. It is perfectly adequate for barrel nuts.

This is what I would recommend as well. A decent adapter would cost this much ($9.99).

I agree with both sides here.  The adapter won't hurt much, but the Harbor Freight torque wrench is a) more than accurate enough, b) affordable even without the discount, and c) easy to check the calibration of if/when you need to.  I wound up buying all three sizes they carry: 1/4", 3/8", and 1/2".  I spent less on all three (because of the coupons) than the cheapest torque wrench I could find at Sears.

I used an adapter on my 3/8" Snap-on wrench to install two of my barrels.
The torque range is HUGE. It's not that big of a deal as long as it's over 30# and the tube lines up.

ETA: I already had the wrench so I didn't have to buy one.

A 3/8” to 1/2” adaptor does not change the torque.
An extension like the armorers wrench does change the amount of torque applied, but the mil-spec torque specification already allows for that so there are no calculations involved.

Also AFAIK it takes well over 100 ft/lbs to strip the threads on a new upper.
I would be more worried about the index pin if I were over torqueing

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