I had a red dot mounted on my Mossberg 500 (smooth bore) shooting the slugs many years ago. I mounted a rail on the receiver, and put a simple 4 moa red dot on it. It worked ok. Accuracy was not bad at 100 yards. My main complaint was the trigger pull. When you go from a bolt rifle to shooting a shotgun like a rifle, the trigger pull was very heavy. With a rifled barrel, accuracy should be better than the smooth bore. But it's doable.