The Adjustable Ranging Telescope (ART) is a weapons sighting system typically used as a military rifle scope which was initially designed for service in the

Vietnam War The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...

. It was developed and patented by James M. Leatherwood. It combines a range-finding scale inside of a

telescopic sight A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. It is equipped with some form of a referencing pattern – known as a ''reticle'' – mounted in a focally appropriate p ...

with an adjustable

cam Cam or CAM may refer to: Science and technology * Cam (mechanism), a mechanical linkage which translates motion * Camshaft, a shaft with a cam * Camera or webcam, a device that records images or video In computing * Computer-aided manufacturin ...

integrated into the scope's mount. This raises or lowers the rear of the outer sight to compensate for the ballistic rise or fall of the projectile. The cam is preset for a specific cartridge, i.e., the 7.62 mm NATO round. Since the range cam is locked to the magnification ring, it automatically sets the range and adjusts for the ballistic drop of the shot. This then allows the shooter to place the optic's aiming point directly on the target. During the Vietnam War, Lieutenant Leatherwood, who already had the patents for his ART system, entered the Army and began working with U.S. Army Ordnance specialists. The combination of the Leatherwood Adjustable Ranging Telescope (ART) with M14 National Match rifles went on to create the M21 Sniper Rifle.

References

Firearm sights {{optics-stub