SG, good advice from both HM and Bruce, but I'm assuming you already have a rifled slug barrel for this gun?? If not and you need to buy a slug barrel, I would recommend a fully rifled cantilever scope mount barrel. That way you have a barrel with a permanently attached scope that you can remove without upsetting your point of impact, allowing you to use the gun for other types of hunting. Otherwise, the saddle type mount that Bruce suggested is the way to go. There is a company called B-Square that makes a really nice saddle mount, but it comes with a good set of rings also for $50 total. I've put 3 of these units on guns for other guys and they all like the way they are shooting. If you need more help, post again with a little more info like what barrel you are going to use, and I'm sure we could help with slug recommendation, etc.