Ar10 barrel nut shim


Oct 24, 2012
Central Texas
I'm trying to install a free float tube on my dpms lr308 and I can't get the nut to line up with the gas tube hole. I have searched for a shim or an alternative with no luck. I need help! Thanks

What are you torquing it to? Several different styles out there, so some pics may help. Many of them are just a bit different, but you should be able to torque the nut far enough to get one of the holes lined uop with the gas tube hole in the upper. Use an alignment tool to verify this, but that's where you want it to be.

And no, there shouldn't be any shims involved in this.
I am less than 30 lbs when I go past one hole and am at 80 before I get to the next. I might add that it took a ridiculous amount of torque to get original barrel nut off.
You'll note that most of the build guides (okay, all of them) list a minimum spec for torque, but virtually none list a Max. You want to run in up to the spec'd minimum torque figure, and then past that mark to the next hole that aligns. I'd recommend using a good anti-seize as lube, and doing the whole torque it up/back it off routine at least three times before the final installation.

Give that a whirl, and it should work for you.
I doubt you'll go that much, but I've seen several that were dancing arounf the 80 range. Do the torque/back off drill at least three times, and you'll lessen some of the stresses a bit. And don't forget the anti-seize!
Another option is to take a skim cut with a lathe on the interior shoulder on the forend. Just a thou or three would be about right.... That said, torque as stated three times or so, and snug er up to that next hole...some of them can be quite a lot to get to the 'next' hole, and the one previous is just too loose.
Thanks msalm. I thought about lightly sanding the edge to get a little more rotation on it. This is a used free float tube and it has a rail mounted on the bottom of the tube for a bipod, of course now that's not going to be centered when I get it all tightened down. I guess I have a lot to learn about ar building :) thank you both for the advice.
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