Over torqued barrel nut... upper receiver or barrel nut ruined?

[M4Fundi]

So my torque wrench is not clicking and I have no idea what I torqued a Geissele barrel nut to a VLTOR upper receiver. When it felt wrong I stopped and backed it off with a breaker bar. So, I don't know if I over torqued it or not, but if I did is the receiver or the barrel nut ruined? Any way to check? I am headed to Home Depot right now to buy a better torque wrench!

[Todd.K]

Inspect the threads of both, and the face of the barrel nut that contacts the barrel extension for deformation.

I believe your barrel nut is aluminum so either is possibly damaged.

[M4Fundi]

Sounds like a plan ! Thanks!

[M4Fundi]

Barrel nut is pristine and receiver looks fine. Thanks!

[markm]

You really have to crank on a steel nut to wreck an upper that's 7000 series forged. I only use a torque wrench on fragile systems. Your arm will tell you the correct value after building a few guns.

[SteveL]

I agree with MarkM. I would be surprised if you did any damage to either part. Use some moly grease or anti-seize on the threads and tighten and loosen the barrel nut a few times before doing a final torque.

[markm]

Vltor had a few systems where they welded 6000 series to make a "monolithic" upper/rail system. I used the torque wrench on those to keep it under 40 or whatever their spec was. Other than that, my torque wrench gathers dust now.

[Stickman]

Big important part right there that you don't want to overlook.... GREASE that pig before you tighten it down all the way (3x).

As usual, I agree with Todd. There shouldn't be any issue.


Todd- A little while after you left one of the low hire monkeys shattereda old Vltor upper of mine.

[Hammer_Man]

Most 1/2” torque wrenches don’t go any lower than 50 lbs, so you’re not going to get a click on a fastener that only requires 30 - 40 lbs. I used a 3/8” torque wrench with a 3/8” to 1/2” adapter for a long time. Never had any issues with that setup. I had a Snap-On digital torque wrench that could go down to 30 lbs, but that’s overkill for at home gun smithing. I recently picked up a $21.00 1/2” torque wrench at Harbor Freight that goes down to 30 lbs, and that’s what I’ve used on my last build. Lastly, always grease the threads with a moly grease before assembling.

[Disciple]

You really have to crank on a steel nut to wreck an upper that's 7000 series forged.

I was curious, and checked https://www.engineersedge.com/torque_table_sae.htm which indicates that one may torque a 1" fine thread 2024-T4 bolt to 166 foot-pounds. The larger 7075-T6 thread can probably take quite a bit more even with shorter than standard thread engagement. I wonder if something else would fail first.