I have a 16" post ban RRA upper with muzzle break. I want to install a NM barrel. I have a couple questions. If I pull off the 16" is the barrel nut reusable? Seeing that it won't come off easy. What esle will I need beside barrel, gas tube and handguard. I'll be going with the RRA barrel. I've never done this before, but I'm very handy. It seems easy from some of the posts I've read. Thanks.

If your post-ban brake is welded on, don't bother to try to salvage the barrel nut.  Just get a new one with your new barrel.

RUSS4777
Will I be able to use the barrel nut again if I go back to the 16"?

you can reuse the same barrel nut several times --just make sure there are no debris on the seating surfaces..ok [brick]