"One of the things that made the M21 a successful sniping system during the Vietnam War was the ultra-simplistic means of range estimation that would also automatically adjust the scope for ballistic drop at whatever range the scope estimated the target to be at. This was known as the Auto Ranging Telescope, or ART, and it was designed by James Leatherwood. These original ART setups on the M21 used a Redfield 3-9x scope and there were two distinct versions of the setup through the M21's life time. The Leatherwood name now appears on a very similar setup to the original ART and it is the same concept and even carries the same ART title, but are they as effective as the original? There is only one way to find out." - SNIPER CENTRAL
To read their full review and comparison to the Vietnam era ART scope... click here!