Al in Mi wrote:it shouldn't be a problem to cut off the the threads, your local gunsmith or buddy with a lathe or a mill, should be able to get it done.
This was my thought. At the risk of causing mental scars to those of you in free states, my newest bright idea was just getting the Bushy 20" upper and having the barrel cut back and crowned by ADCO. Since that's what I was looking for originally (a barrel without threads), that seems to be a smart idea, especially if I can get the complete Bushy upper cheap.
ETA: @Jeepejeep: ATF rulemakingsays that welded muzzle devices become part of the barrel and thus "remove" the threads. The rest of the state sticks to that (hell, my tactical AR is a 14.5" barrel with a pinned device that brings it up to 16", meeting both Title 1 length and AWB compliance - built by a 07 up here, so definitely legit) but I totally hear you, since I've heard about that nonsense you've got going on down there in the shadow of NYC. For me, I'd sooner just cut/crown the barrel on the .450 than have a permanent device.