English: The 20mm M61A1 Vulcan built by General Electric was a standard aircraft gun used by the USAF. Based on the premise of the multi-barrel gun first generated by Dr. Gatlin in the nineteenth century, the Vulcan was equipped with a rotary action and was tied into the aircraft's hydraulic or electrical system. The Vulcan fired about 6,000 rounds per minute and had a high muzzle velocity of 1,036 meters per second. Initially the ammunition was fed into the cannon on a belt but the reliability was low and there were problems with the link disposal. So GE designed the Vulcan cannon with a linkless feed system. The ammunition drum could hold around 1,000 rounds and was attached to the cannon by an ammunition conveyor belt.