I always zero my rifles at 100 yards. My load ,out of my 243, zeroed at 100 yds drops 21 measured inches at 400 yds. Zeroed at 200 yds the group prints 1.5 inches high at 100 yds so by subtracting 1.5 from 21, it should print 19.5 low at 400 yds. I am told by a friend that I can't figure it that...