Hi

I have a Bushmaster lower with a fixed CAR stock and I am having a heck of a time trying to remove it.  I cannot get the locking nut to budge with my spanner wrench.  I have soaked it with penetrating oil overnight and it still won't move.  It is on so tight that the nub on my spanner wrench looks like it's going to break off.  I know this is probably not the best thing to do, but I even tried turning it with a pair of channel lock pliers and it still won't move.

Any help would be appreciated.  When looking at the rear of the receiver, I am turning the nut counter clockwise (lefty loosey).  

Cheers

Use a heat gun to break to heat the receiver extension two inches back from receiver to 600*.  The receiver extension may have been installed with loctite, and the heat will break the bond.