Ok, fairly new to building guns, so please keep this in mind.
Yesterday, a friend asked me to help him put a DD rail on his gun, a fairly new Colt AR.  I tried for the life of me to get his barrel nut off....never had problem with one in the past.  I pulled and pulled on it with a DPMS wrench and thought I was going to break the block holding it in the vice.  Eventually, when I started breaking teeth on the nut itself I decided to go for a different approach.
What I am looking for is did I screw anything up or is this just one of thoes things that happen when working on ARs.
What I ended up doing was getting the Dremel out and making a cuton each side of the nut (after cutting off the locking collar and removing the coil spring with pliers.  After cutting I took a flat head screwdriver and poped it, then finnished up unscrewing it with the wrench.
When removed I noticed I went a little deep and cut accross the threads on one side, about as deep as the threads were.
After this the new barrel nut went on with out problems and I cinched it up to 60 lbs.  I told him that if there was any problems I would buy him a new upper (because after all I messed it up).
My question guys.....is did I screw the pooch on this, and need to start pricing uppers?  And what would you guys with more expierence have done with the nut....remember I was putting some serious torque on this bad boy and started preaking teeth on the nut itself.

Thanks for the advise,
Romper

Well worst case, you'll only have to spend $80-$90 on a cerro forged upper. Im not the resident gunsmith but it sounds like the thing seized. Did you try lubing/heating etc?

Broken teeth happens sometimes.  Sometimes those barrel nuts can be unbelievably stubborn.  I would have tried heat and some penetrating oil before taking the grinder to it, but that's just me.

As far as the threads go, I'd shoot the thing and see what happens.  My guess is that it'll be just fine.

if you just cut into threads on one side to the depth of threads and not thru reciever and you torqed new barrel nut to 60lbs with out pulling threads you will be fine . you should have heated barrel nut and it would have came off but your way worked

Thanks guys, didn't have access to a torch....so I used the only thing I had availible.  I did think about heat, just didn't have access to any.  O well, live, build and learn I guess.
This was about the toughest nut I have ever had....was wondering what the hell.  Anyway used some wheel bearing grease on it so next time we souldn't have this problem.

Romper