RE: Shotgun Scope help
I prefer regular scopes. I believe getting on a target that is moving may be easier with a red dot but I generaly don't take those shots anyway.
I do have a Simmons scope on my 870 and love it. It has the diamond reticle. This is great because you can have an aditional mark for greater distances (bottom of diamond) I also know with the diamond you can somewhat range things at distance by thier size realitive to the diamond. I haven't put to much time as all my shots have been under 100 yards. Well actually under 80. But the gun/sllug setup can reach out there pretty good.
So I guess something like mine would be my recomendation. I think it was around 100-150 at walmart once apon a time. But its been years. Probably not the best scope on the marked but I've had great luck with it and have had it in some crappy weather and bounced it around plenty and never had a problem.
Good luck with your decision.