I have a Mossberg 20g Super Bantam I want to put a Red Dot Scope, what kind of mount do I use.
You may want to try the aim tech saddle mount type mount. I have my red dot on my 870 with this type mount and have enver had any issues.
If your gun is drilled and tapped already I would suggest putting a rail on it and mounting to that.
If your gun is drilled & tapped, this should work on yours I would think. I just ordered one for my 535 to mount a red dot on it.
http://www.amazon.com/UTG-Weaver-Picatinny-Tactical-Profile/dp/B001WIYQNG
I have a picatinny rail that will fit your Mossberg if you are interested.