I was installing my barrel and cranked down the vise.  I have two mounted vise.  The big one is currently covered.  I figured the littler one would do the trick.  I started the procedure with no trouble. I torque it to 30ft/lbs and backed off, then again to 30 ft/lbs and backed off.  I then started to torque down the barrel nut.  The barrel was twisting a little, so I added a little more pressure to the barrel.  I then started to torque the barrel nut again and BOOM the vice broke! What the heck was that about?  

I then cleaned off the other table which took three hours and finished off the barrel nut with the large vise.  I still had a little problem with the barrel twisting so I used the leather strip idea, worked great.  Got to 70-75 ft/lbs when the last hole in the barrel nut lined up.  Job came out great.

Thanks to all at AR15.com for help.