I have a 870 Express Super Magnum or whatever the one that shoots 3 1/2" shells. I've had a lot of issues with it jamming very often and can't say I like the gun a whole lot. That seems to just be me though as lots of others seem to have good luck with them. If you want to shoot deer you probably either want buckshot or slugs. Slugs are nice if you want to use it like a rifle however, in a lot of places I use mine to hunt with slug's just aren't the answer so we use buckshot. If I was going to use slugs I'd rather just use the rifle. I use the shotgun with buckshot in places I can't use a rifle or slugs. Anyway, mine seems to like a full choke with Winchester 3" 000 buckshot. Doesn't seem to like 00 buckshot as much in 3" or 3 1/2". I don't know why. It also seems to like lock up the pump and you have to really hit it to get the pump to come back with the shell after a few shots with 2 3/4" shells. I've never tried buckshot in that size but it does that with target shot. 3" and 3 1/2" don't seem to have this problem but they just randomly jam like not kicking the shell all the way out or trying to send 2 into the chamber. Just random stuff like that.

Just thought I'd throw this out there as you may not want a slug gun depending on where you are hunting how you want to hunt and what your local laws are.