I played around with a Remington 870,rifled slugs and a rifled choke tube. I used a Red Dot sight and was able to keep all shots inside a 4" circle at 75 yards. I have a friend that has killed several deer at 60 yards with an 870, rifle sights and a modified choke tube.
You might have to try several different brands of rifled slugs to get the one that shoots best for you but they are pretty inexpensive.