My friend just got a bushy a month ago and just got a free float tube this week. I went to his work with him to help put it on. Well, we put the barrel in the barrel blocks on the vice and try to get the barrel nut off and it wont budge! He finally gets it to budge but instead of it just budging the nut and upper reciever spin together. I know that this is bad because the barrel has a locating dowel that fits into the upper reciever. Anyone have any suggestions? I never had this problem on my colt and I dont know what to tell him.

Next time since the nut is tightened to the receiver try holding the receiver and turning the nut.  Why would you hold the barrel and turn the nut when the nut is screwed to the receiver?

So anyway you obviously sheared the index pin and perhaps widened the index notch in the receiver.  You need a way to hold the receiver in the vise. They make action blocks for this or rig something up, and then the nut will turn off.

IVe used the same procedure for both my colts and had no problems. Ive got an army manual that shows them using barrel blocks in a vice. I know that nut is WAY tighter than 30ft lbs.

I'm with David, hold the upper. You will probably have some problems with accuracy.

There will definetely be some problems using the iron sights now. Thanks for the replies guys. My friend is soooo pissed its like he wrecked a brand new car or something. I felt bad because I watched him do it and couldnt figure out what was wrong...like I said it went smooth on my rifles. Hopefully he wont have to buy a new upper for his new rifle.

If the barrel and upper spin together, I don't think you've broken anything, although the barrel blocks have probably marked the barrel.

For maximum success, you need to use one of the clamshell action blocks that wrap around the upper receiver.

BTW, 30 ft lbs is the [i]minimum[/i] torque for a barrel nut.  You are allowed to apply up 80 ft lbs to align the barrel nut for the gas tube.

If the upper receiver and the barrel nut are turning together, chances are the barrel is also turning in the vice jaw barrel blocks. I'd be willing to bet the barrel is slipping in the aluminum blocks.  Try this tip, scuff the the channels of the barrel blocks with 80 grit, use rosin and or lead shims.  Remember barrel blocks have been around a long time and I've used them without incident many times. I will say they hold the heavey barrels a lot better than the pencil ones.

THIS is exactly why I will not use barrel vise jaws for anything but installing or removing flash hiders and comps.  I highly recommend using an action block for barrel work.