Installing Barrel Problem

[Danimal]

Deleted

[Great-Kazoo]

i tighten by hand, un-tighten then torque to 35-40 ftlbs with out issue. I always use some white grease / lube on the threads prior to assembly. I have yet (key word) needed to torque one that high to align everything.
Do you have good front-rear sight alignment? if not there may be some wear if not function issues while shooting.

[BPTactical]

STOP! You are on the threshold of pulling the threads off the receiver nose!

Jim is on the right track and so are you but even on match grade AR's I have never had to even come close to maximum torque. After the snug and loosen routine to burnish the threads I set my torque wrench to 40 ft/lbs and with moly based anti-seize on the receiver nose torque to 40. Check alignment for the gas tube and if needed apply a LITTLE more torque to line up the gas tube.
Even on disassembly I have never come that close unless some knucklehead Loctited the barrel nut.
Don't be afraid to try a different barrel nut.