Here is a 230 yard smoothbore slug video. Now Hickok45 CAN SHOOT no doubt. But it is not hard to put regular rifled slugs on a 8 inch plate at 100 yards with a smooth bore shot gun with a cylinder or Improved cylinder choked barrel. With the imp. cylinder usually being the better of the two. Smooth bore shotguns slinging rifled slugs are more accurate than one would think.
http://www.youtube.com/watch?v=nNTyCcip-ks
As far as buckshot, I personally wouldn't feel comfortable at more than 60 yards or so. I once took a deer at 70 paces, with 3" OO Buck with a 500 Mossberg 30" barrel Full Choke. I only put ONE pellet in the deer's neck. And he ran a country mile. The only way we found him was with our trail dog (short legged Beagle). It was a dumb decision to even try that shot. But I was young and I didn't have any better sense back then.
