I was at the camp & I shot the gun a few times. All I had was 'high brass' Federal #6 shot, they kicked a fair amount in the light gun. The pattern seemed centered pretty well. After my 2nd shot the front bead fell off, never to be found. Like I may of said, I think the 'chop job' was done after the gun left the factory.
Since there is no rib I am thinking about a sight that slides over the barrel. One at Midway seems to get O.K. reviews. It's a 'tru-glow' type with the light gathering tube. The barrel has a non-threaded hole where the bead was sitting, so I can't just put another bead in anyway. Yes, there is a hole there into the barrel.
I think a light gathering tube would be enough, I don't want to sink $$ for a new barrel or specialty sight. I also plan on getting some very low brass #6 shot, that's enough. I have read where one really doesn't need a sight on a shotgun, but this may be used more for aimed fire rather than moving game.