The M61 Vulcan is a 20mm hydraulically or pneumatically driven, six-barreled, air-cooled, electrically fired Gatling-style autocannon with an extremely high rate of fire. It has been the principal cannon armament of United States military aircraft for five decades. The M61 was originally produced by General Electric, and after several mergers and acquisitions is currently produced by General Dynamics.
At the end of World War II, the United States Army began to consider new directions for future military aircraft guns. The higher speeds of jet-engined fighter aircraft meant that achieving an effective number of hits would be extremely difficult without a much higher volume of fire. While captured German designs (principally the Mauser MG213C) showed the potential of the single-barrel revolver cannon, the practical rate of fire of such a design was still limited by ammunition feed and barrel wear concerns. The Army wanted something better, combining extremely high rate of fire with exceptional reliability.
In response to this requirement, General Electric Armament Division resurrected an old idea: the multi-barrel Gatling gun. The original Gatling gun had fallen out of favor because of the need for an external power source to rotate the barrel assembly, but the new generation of turbojet-powered fighters offered sufficient electrical power to operate the gun, and electric operation offered superior reliability to a gas operated weapon. With multiple barrels, the rate of fire per barrel could be lower than a single-barrel revolver cannon while still giving a superior total rate of fire.
- Main article: Peace Walker Incident
Big Boss was the first to encounter these weapons, with the AI weapon Cocoon's fearsome battery of weapons including a half-dozen rotary cannons of around the correct scale to be Vulcans, though they were never named as such.
During the rescue operation at Camp Omega, Big Boss encountered four more M61 Vulcans in towed M167 Vulcan Air Defense System (VADS) installations, protecting possible landing zones for the MSF rescue helicopter. Later on, the Militaires Sans Frontières was hired by the United States government to destroy at least three of these installations as prep work for an attack on the camp by U.S. Marines.
- Main article: Shadow Moses Incident
Years later during the Shadow Moses Incident, FOXHOUND member Vulcan Raven used the M61A1 as his weapon of choice, with a customized mounting that let him carry it as a personal weapon. The fact that he was capable of lifting the 248-pound gun, power supply, and heavy ammo drum (which all in all should weigh as much as a car) by himself, and could withstand the recoil which should be like a jackhammer, was a testament to his incredible strength.
Vulcan cannons were mounted in Phalanx CIWS installations on the Missouri during the time of the Guns of the Patriots Incident, and were used along with her 5-inch / 38 caliber Mark 12 dual purpose guns to protect the aging battleship from a volley of Harpoon anti-ship missiles fired from Outer Haven.
Behind the scenes
Vulcan Raven's M61A1 appears in the original Metal Gear Solid. The name "Vulcan cannon" has often been used as a generic term for rotary cannons throughout the Metal Gear series, including the armaments of TX-55 Metal Gear, Metal Gear D, Metal Gear REX, and the Hind D.