200 yards. Think Caterpillar and 25-30 wide. Why: Necessary for sighting in purposes. You'd be surprised to look at a 20 ' backstop/berm and how little safe area it offers from 200 yards away. Better to be a little over-size on your berm than have a high power bullet get away from you down range. Just my unbiased opinion is all.
Watch it!!! their both out to get us.