Both my brother and I have 204 AR's. We ended up fouling the barrels out on both of them. You got the barrel used, so have no real idea how much it was shot before you got it. I would spend some effort cleaning the barrel over a couple weeks and see if you can get it to start shooting. My brother got his back to driving tacks, I still need to work on mine.
My local dealer just got in a 20 Practical Encore barrel. I have thought about it a little.
Bob R