I have a no-name LR308 upper that I can't seem to time the barrel nut on. I should probably toss it into Lake Washington and buy something better, but before I do that, I may give shims a try. I have found a few sources for shims, but I am kind of surprised to see very little discussion of the use of shims to time the barrel nut.

Is this a common practice?

I got mine in 2 days from Amazon

Depending on what type of barrel nut it is, and the purpose of the timing (assuming it's for proper alignment of a free float HG?), yes.

Aero Precision sells shims for this. Some of their HG/barrel nut combos require them.

Optics Planet will have shims too.

Not being sarcastic, but look for a handguard that doesn't need the barrel nut to be timed.

I

Have been tired of timing so I did the homework and found the alternative solution, I can sleep better now.

That may be the route I go. I was trying to do a slightly retro build with a delta ring/A2 handguard, but I guess having as rifle that functions trumps that desire.

I may have some shims. I’ll have to look when I get home tonight.
I’m a fan of retro builds. I got more than just barrel nut shims inside this project

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You can also lap the upper to get it to line up

Why are you needing shims if you're using a GI barrel nut? Just get it to the midrange of the torque spec, and tighten to next notch. Or without a torque wrench, just do the "tighten three times, then align" method.

Never heard of anyone needing shims with a GI nut. I've never needed them.

I think I was just unlucky with this particular receiver. At 30 ft lbs, one 'tooth' on the barrel nut just starts to interfere with the gas tube, and when torqued to 80, that same tooth is still in the way.

That's a pain. Me, I'd just go ahead and turn further to next notch. Also heard of folks just dremeling off a tooth to accommodate.

Well, I got ahold of some shims, and although they probably would have been fine, I just didn't like the way things were coming together. So....Aero Precision M5 to the rescue.

The rifle is retro but not retro. 18" faxon pencil profile barrel, and an ASR brake will grace the muzzle. I'll probably go with an LPVO of some kind 1-6 or 1-8.

I'm happy with it. It's very light. I may still go with a round A2 style handguard if I can find one in OD. Lots of places are sold out.