RE: 12ga or 20ga
I have a H&R Ultra Slug Hunter 20 gauge with a scope on it and at 30 yards i shot 3 times and only made 1 hole. i'd say thats pretty good, then i got back to about 100 yards or so and shot twice more, my farthest shot from the bullseye was 3 inches. I am very happy with it! I wouldnt be afraid to make a 130-150 yard shot with it at all!
Oh, and I shoot 2-3/4 inch winchester sabots.