I just bought one from the Local Gander mountain they still had Two more on the shelf paid $79. for it its an all purpose 18.5 just in case barrel, They do store tranfers and if you call them they will ship it to you at a cost. Rochester, MN
I've considered doing that, but isn't it rather expensive to thread a choke? For that matter, making it a 20" i assume your either making a slug gun or an HD gun and wouldn't an open bore almost always be better for what you use it for anyway?