My Remmy 597 is a smooth bore now after 40,000 rounds. It shoots about 2"-3" groups at 25 yards now. I used to be able to hit bottle tops at 100 yards with it when I was a kid.
If you CLEAN IT regularly, it's probably a Smooth-Bore from the Cleaning Rod contacting the BORE--And if not, it's probably NOT really a Smooth Bore, it's just ALL LEADED UP! LOL!....mikey357