M61A1 Vulcan Cannon The M61A1 Vulcan cannon is a six-barrel 20mm weapon capable of firing 6,000 rounds per minute. Incorporating the same basic principle invented by Richard J. Gatling in the 1860s, the M61A1 multiple gun barrels rotate rapidly to allow a high rate of fire. Because each barrel fires only one of every six rounds, the wear and heat generated are less than with a single barrel gun. Vulcans can be driven electrically, hydraulically or by a ram-air engine. In service since the 1950s, the Vulcan has armed such USAF aircraft as the F-104, F-105B/D/F, A-7D, F-4E, B-58, B-52H, F-15 and F-16. Also, aircraft lacking an internally mounted gun could carry a ram-air driven M61A1 in an external pod. Before coming to the museum, the Vulcan on display was carried internally on an F-4E Phantom II assigned to the 1st Tactical Fighter Wing at Langley AFB. The 1st Fighter Wing currently flies the F-22 Raptor armed with the lighter M61A2. Click here to return to the Cold War Gallery.