I would recommend a variable power scope that starts around 1X or 2X at the most. If you hunt in brush at all, 4X is a mite too much for my liking. Your question of "What range would this setup be lethal to" is only answered by YOU spending a lot of time at the range. Do NOT use anyone's numerical answer on this board. If you can't hit a 6" diameter circle every time at 50 yards at the range, then it is less than 50 yards. If you can keep them all in a 3" circle at 100, great. As far as energy goes (lethality), it depends upon each slug, but usually (not always) your marksmanship is the limiting factor. Most slugs have enough energy at 100 yards for a humane kill. I would recommend that you try a lot of different brands as was suggested and my opinion is the 2 3/4s as well. But you never know what your gun will like, so try the 3s also. I would really recommend a shooting vise for siting it in, it is a better way to go and much more pleasant. Best of luck to ya.