This is a reply to an older post, but I thought I would bring it up again.  If you have the equipment and ability to true up a barrel nut, you should just dump the factory one and build your own.  Everything will be centered, and you can start your inside thread cut and take 3 or 4 passes, then finish out with a good tap by hand. Now you have a square and true nut that you can fit to the action OD. I just did one for my Stiller P-1000 large... 1.550 ins. I know it's as true as the action and the threads are clean and true.  Use a taper tap, not a plug tap.
				
			 
	








 
			 
			 
			 
			 
 
		 
			 
			 
			 
			 
			 
			
