You asked "what kind of slugs?"
With a smooth bore, the key is to not use Sabot Slugs, they are designed specifically for rifled barrels. Use "rifled" slugs. In my experience, the Brenneke KO's kick some serious butt from a smooth bore with rifle sights. I'm with most here, 75 yds is a reliable maximum. If your going to 100yds, be well practiced and confident in your ability.