Doing a rebuild of a shotgun. It's a wood stock, has a busted bolt. I was thinking about removing the barrel and action and modifying the stock to accept a barrel and action in semi auto, detachable magazine setup. I thought it would be a fun build. Problem is, I don't know where to find just parts so I can build my own. I can find plenty of semi auto shotguns, but I want to build it not buy it. Where can I find the parts?