I have a mossberg 500 .50 muzzleloader barrel. It swaps out very easily and converts your 500A into a muzzleloader. These cost $130 new. It came with my gun when I bought it from an individual. I have never fired it. $75 shipped SOLD!!! Pending payment.
I have one of these, and I like it a lot, BUT, I don't really like the primer position. It's a ***** trying to place/replace the 209 primer. My fat fingers just don't go in the ejection port very well.