Hello all, this is something I've been wondering for a couple years but just now around to asking

I bought a spikes upper receiver a couple years ago brand new for a 300blk pistol build. At the time, I got a MI ff handguard to mate to it with an 8.5 barrel. Back then, I had to tighten the barrel nut to about 83ftlbs in order to get the gas tube aligned into the upper. Well a couple days ago, I decided to throw in a colt 14.5 m4 barrel I had lying around that was from a 6921 upper for a spare parts gun, and found that, yet again, I had to align the nut at a tad over 80flbs. About 83-4 I think. Is it possible my upper has been out of spec all this time? This same barrel came matched to a colt receiver at around 50ftlbs, and went back on at around that torque as well. Any help would be apreciated, thanks.

And I tightened to 30, loosened, 35, loosened, 35, loosened, then do final torque same as the rest of my uppers. Only receiver I've ever had this issue with.

It doesn't mean anything is out of spec, sometimes shit just doesn't work perfectly.  I had one upper that experienced the same issue.  I tried a spare barrel nut a friend had and it worked fine (think it aligned somewhere around 50-60 ft. lbs.).  It should also be noted that particular upper came as a complete assembly from PSA and the stock barrel nut lined up fine at a much lower torque value.  They also sell barrel nut shims for this issue which would help it align at a lower torque value.

Truthfully, you're probably fine at the current torque level.  If it really bothers you, try another barrel nut or pick up a pack of shims.

Not an issue. Don't worry about it.

If you loosen it again, the next alignment won't take as much pressure. Something around 70 pounds of torque is considered maximum for an AR15, but a few pounds more won't ruin a thing.

Whatever you do use smooth even pressure when applying the torque. Jerky movement on the wrench will cause damage when using this much pressure.

I've had this happen enough that I keep shims on hand all the time now, and shoot for alignment at 45 ft-lbs.