The manual says this specific nut on the AR 15 should be torqued to 40 foot pounds. 40, not 400 and it was staked too. Trying to remove it put me back into the days in the Navy and a BFH (using a bigger fucking hammer) to free this castle nut. I failed miserably and then needed to enlist professional assistance to loosen this. Note to manufactures who write the manuals and specs- please follow your own advice!