The Ford-Philco

Philco

Philco, the Philadelphia Storage Battery Company , was a pioneer in early battery, radio, and television production as well as former employer of Philo Farnsworth, inventor of cathode ray tube television...

 GAU-7/A was an abortive program initiated by United States Air Force

United States Air Force

The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

 in the late 1960s to develop a new cannon

Cannon

A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...

 to replace the M61 Vulcan

M61 Vulcan

The M61 Vulcan is a hydraulically or pneumatically driven, six-barreled, air-cooled, electrically fired Gatling-style rotary cannon which fires 20 mm rounds at an extremely high rate. The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft...

 on the then-upcoming F-15 Eagle

F-15 Eagle

The McDonnell Douglas F-15 Eagle is a twin-engine, all-weather tactical fighter designed by McDonnell Douglas to gain and maintain air superiority in aerial combat. It is considered among the most successful modern fighters with over 100 aerial combat victories with no losses in dogfights...

. The GAU-7/A was a 25 mm Gatling gun

Gatling gun

The Gatling gun is one of the best known early rapid-fire weapons and a forerunner of the modern machine gun. It is well known for its use by the Union forces during the American Civil War in the 1860s, which was the first time it was employed in combat...

 using telescoped ammunition

Telescoped ammunition

Telescoped ammunition is an ammunition design in which the projectile is partly or completely enveloped by the propellant. Examples include ammunition for both hand weapons and artillery.-External links:*http://www.veritay.com/defense/def_ammo.htm...

 with a combustible case. It was intended to have greater range and hitting power than the 20 mm Vulcan, while the caseless ammunition would have alleviated the problems of either storing or ejecting spent cartridges, both of which present considerable problems for jet aircraft. Despite great expenditure, the project and its ammunition proved to be a failure, and it was canceled in 1974. The F-15 therefore retained the M61A1 cannon, as have most U.S. fighter aircraft

Fighter aircraft

A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...

since 1956.