I've only shot mine to 400 yards (longest my personal range goes).
Once I got the sight adjusted where it hits at 100 yards when it's set on the 100 mark, its on at 200, 300 and 400.
Maybe this spring I'll take it out and see how it works at farther distances.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071