Is it time to try some barrel nut shims?

[MistWolf]

OP couldn't get it to line up between 30-80 with no shims, he added 2 shims and got it to line up at 52... adding shims, like timing a muzzle device, does not necessarily mean more torque, it can mean less.

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The barrel nut lined up on the first notch at a torque value below minimum. To align the second notch required a torque value above maximum. Adding two shims means the barrel nut will tighten sooner, which allowed the barrel nut to align with the first notch at 52 ft/lbs. Removing one shim would allow the first notch to align at a torque value less than 52 ft/lbs.

The only way adding shims will reduce the needed torque is if so many shims are added that the notch before the first notch comes into alignment. That's more shims than are needed for the job.

If the receiver was faced instead of using shims, then material would need to be removed until the second notch aligned at the desired torque value

[LMT/556]

I had a BCM receiver/standard barrel nut do this. 30 had a tooth beginning to cover the hole, the next timing groove had my torque way high even though the mid-length shot fine. I ended up sending that receiver back due to an out of spec top rail that caused and interference fit with Geissele mount lugs. BCM replaced the receiver and the next one torqued at around 40 IIRC.

Two established builders I discussed this with both stated not even using torque wrenches, they tighten to the next timing groove and generally have a feel if something is off. Generally I'd wager they have additional stock to try if something feels off.