My family has a small (11 acres) property that i can legally hunt with a rifle, but I choose to hunt with a slug gun.

I use an old beat around 870, with a barrel cut off to 18.5" and a cylinder bore and a red dot. I am consistently getting 3" groups at 50 yards with any slugs tested, but it actually likes the cheap Herters (Cabela's) slugs best for accuracy (around 2" groups at 50) the next best is the old classic Remington sluggers. pick up a few different boxes of slugs, take them to the range and see what your gun likes best and use the most open choke you've got. Most slugs are designed to give the best accuracy out of an IC choke, but will still give good accuracy all the way up to Modified.

Edit to add, for smooth bore don't try to go with any of the sabot style slugs. they are all designed for rifled bores and will give very disappointing accuracy from a smooth bore, as well as being considerably more expensive. just stick with a traditional Foster or Brenneke style.