I'd go with the 870 and get a rifled barrel with the cantaleavered mount. It'll cover all your needs. The scope stays with the barrel and all you have to do is change from small game season to the deer barrel. Just make sure to check your zero , one shot should tell you. I'd also go with either Lightfields or Rem Copper solids. I can actually use either as they both impact within a half inch at 100yds. Don't forget to just sight in your slugs 2"high at 50 yds and gravity will take care of the rest at 100. After that check the ballisic's chart on the back of the boxes. You should be good to go out to 125 if shooting further I'd hit the range to verify POI. However I' shooting my shotguns less and less and using my muzzy instead.