The ART scope technology was born out of necessity in the early years of the Vietnam War. Enemy snipers were killing American servicemen, but the US Army was not adequately equipped to deal with the problem.
The solution was to send newly trained snipers into battlefield service as soon as possible. However, sniper training at that time was a lengthy process that required long hours on the range teaching recruits to estimate distance and to use the proper amount of “hold-over” (aiming high to compensate for bullet drop) in order to make successful first round hits.
In the late 1960s, Second Lieutenant James M. Leatherwood entered the Army, and brought his recently patented design for a ranging scope that would raise and lower the rear of the scope similar to an open sight.
Shortly after, the Army equipped their snipers with Leatherwood System scopes. The use of the new scope system had dramatic effects.