What's the best way to remove a stuck LaRue handguard nut?

I put a 20" on a build I did recently because I couldn't come up with a 16", now I've come up with a 16" Colt barrel and want to change the original out for the shorter one. Put a LaRue free float handguard on it origin'ally and followed the instructions to the "T" now I broke a DPMS barrel nut wrench triying to get the thing off and my military wrench doesn't have long enough fingers to reach far enough into the flange. Soak it in penetrating oil for a while? HELP! All help appreciated.
Steve