Wynne, correct me if I’m wrong, but you don’t have to have your rifle “zeroed” at 100, right? If you know 2″ high at 100 is on at 200, you can sight in at 2″ high, as a guess of course, no measuring allowed. Then hold over at 300. Or you could have 300 zeroed and hold under at 200. Or do you actually have to be zeroed at 100?