Just ran across this post. I am going to assume that the deerslayer is a smoothbore. Iv'e used slug guns for over 30 years. It is very true that different guns like different slugs. You have to try until you find one that works. The sabots will not work with a smoothbore. One slug that I have seen work very well in a lot of guns is the Winchester super X 2 3/4". That slug worked very well for me in my smoothbore remington 1100 with rifle sights and a scope that was custom mounted to the reciever. At 100 yards I would print groups of 1 - 2" very regularly. Sometimes with holes touching. I used Ironsighter rings so that I could use the rifle sights in case the scope was fogged up. I'm sure that I harvested more than 40 deer with that setup, at ranges from 20 to 125 yards. Unfortunately my favorite gun was stolen about a year ago. I just replaced it a week ago with another 1100 synthetic stock with a rifled barrel and cantelever scope mount. Now I will have to go to the more expensive saboted slugs.
I prefer to use the gas operated semi auto because it takes some of the kick out. Also you already have a bullet chambered for a second shot. I have had several people that I know over the years miss with the first shot and the deer still be standing there, but then spook when they had to rack another round into the chamber. There are lots of good slug guns out there but I wouldn't give up on yours yet without trying some other ammo.