A while ago I bought a Switchblock Upper with the Stainless barrel and SWS rail. I hadn't shot it in awhile and noticed that some surface rust had developed on the barrel. I decided to take it apart and bead blast the barrel.

The barrel nut took quite a bit of effort to get off, but I was able to do it. I got the bead blasting done and started to put it back together. I decided that since it required so much force to get the nut off it would probably be better to buy one of the Geissele Reaction Rods to put it back together (since receiver vise blocks won't work with the MUR). I ordered one and started to torque the barrel nut using the rod.

To get the barrel nut to index correctly for the rail I had to put a significant amount of torque on the nut. I finally had the holes lined up correctly so I started putting everything back together. After inserting the BCG, I noticed it would not fully engage because the lugs on the bolt were not aligned with the splines on the barrel. After fearing somehow I messed up the barrel extension, I tried to take of the barrel nut to investigate. When I inserted the Reaction Rod and tried to torque the barrel nut back off, I felt the barrel extension shift back into place. From there the BCG would engage fully.  

So at this point I am just wondering what I should do because I think I have a somewhat loose barrel extension. I emailed Noveske and the tech guy emailed back:

"I have seen this happen a few times with the reaction rod. What happens is the barrel nut gets tight and rolls the upper around the barrel. This usually ruins the upper due to the extensions pin pushing on the index whole on the upper. The only remedy is to get a new upper and I can help you with that. Unfortunately we do not warranty this kind of thing but, I can sell you a MUR for cost. I hope this will help you out."

Anyone experienced this before? These SWS barrel nuts are a real pain.

I think it is loose but the Noveske guy seems to think the whole barrel is turning. I called it a night after what I detailed in the post. It is a stainless barrel so the barrel is not coated, but I believe the extension is (I didn't bead blast the extension).

did you use aeroshell grease when torqueing the barrel nut ... it is also recommended to torque the nut then loosen then torque it again and do this 3 or so times ... the index pin and u notch are not often a perfect fit and has a little wiggle room