Currently I have a AR15 with a Bushmaster 16in Dissy Upper. After the ban I would like to replace it with a 20in Government type upper.
Should I get a barrel and change the Dissy out?
What parts would I be able to reuse from the Dissy?
Any of the crew from East TN have a barrel vice that could help me change it?
Should I sell it and get a new 20in government upper?
Well fire away
A Bushmaster 20" chrome-lined gov't profile barrel is around $195.
A barreled upper is more, obviously. too many variables on what you'd be able to get for the old upper in resale, so no comment there.
If your upper is in good shape, and your bolt isn't too worn, if it were me, I'd swap the barrels and probably keep the old one as a spare (minimal space required for storage, and worth more to me than I'd get for it on the EE, probably)
The barrel would come with a front sight base (installed) and a barrel nut (with a bayo lug and 1/2x28 threaded muzzle)
Your current delta ring assembly would switch over, as would handguards and gas tube.
You may need a new gas tube roll pin and rivet for the font sling swivel (possibly).
If your dissy doesn't have a standard (unscrewable/removable) muzzle attachment or if you want a (A1 or A2) flash suppressor, etc. you may need one of them as well. You may also need to swap out the front sight post, spring and detent (not sure if the BM comes with one, some "barrel only" suppliers don't include them)
After that, changing a barrel is just changing a barrel (you'll need a barrel nut wrench -- the GI spec wrench is about $10-15)-- just remember to install the delta ring assembly on the new barrel nut before installing the barrel.
I've used receiver blocks to hold the reciever, as well as wood blocks for a barrel-clamp in a standard vice, so either works for a single barrel swap.
If you haven't done it before, it can add to the pride of ownership in the resulting piece, as well as an appreciation for how its built. It can also be dangerous in that once you learn how easy it is, its hard not to want to do it again. And again...
DOH! (I knew that, really!)
ETA +$10 for a rifle-length gas tube.