The General Electric M61A1 Vulcan is a 6-barrel 20mm cannon of the gatling-type. It fires standard M50 ammunition at 6,000 rounds per minute (rate selectable in certain installations).

In 1947 the brand new USAF made a request for a new aircraft gun. The lesson of WWII was that the German, Italian and Japanese fighters could reach out and touch the Americans with their cannon main armament, while the latter had to get up close and personal with the .50 cal main armament of the P-51 and P-47. The 20mm Hispano carried by the P-38 was a relatively low velocity weapon. The idea of hooking up unlimited ammo to a late 19th century "Gatling" type weapon, and powering it electrically was attempted by the US Navy for use on their Torpedo/gun boats. Results were high rate of fire and a high rate of barrel wear out. With propellants of the time and period metallurgy it was a good idea but one that was not ready until new technology came along.

In 1950, the US General Electric Company began designing a cannon for USAF fighters under the Vulcan Project, based on the multi-barrel concept pioneered by Richard J. Gatling in the 19th century. The Vulcan was first fired in pre-production form in 1953, and made its first flight in the Lockheed F-104. Initial problems with the gas bleed resulted in a temporary suspension of firing tests, until a better venting system for the F-104 gun compartment was designed.

Today, after a period of neglect (when guns were thought to be rendered obsolete by missiles), the M61 in one form or another, is an integral part of the armament of modern fighters such as the F-15, F-18 and of course the F-16.

Recently, GE's armament division was acquired by Martin Marietta, so the M-61 is now officially known as the Lockheed-Martin M61A1.