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.