continuous fire from a conventional single-barrel weapon ordinarily results in rapid barrel heating followed by stoppages caused by overheating. In contrast, a five-barreled machine gun firing 1000 rounds per minute fires only 200 rounds per barrel per minute, an acceptable rate of fire for continuous use. The only limiting factor is the rate at which loading and extraction can occur. In a single-barrel design, these tasks must alternate; a multiple-barrel design allows them to occur simultaneously, using different barrels at different points in the cycle. The design also solves the problem of defective ammunition, which can cause a normal machinegun to malfunction when a cartridge fails to load, fire, or eject from the weapon. As it is powered by an independent source, the gun simply ejects the defective round along with the rest of the cartridges while continuing to operate. Models M61 Vulcan and other designs The M61 Vulcan 20 mm autocannon is the best-known of a family of weapons designed by General Electric and currently manufactured by General Dynamics. The M61 is a six-barreled 20mm rotary cannon that fires at up to 6,600 rounds per minute. Similar systems are available in calibers ranging from 5.56 mm to 30 mm (the prototype T249 Vigilante AA platform featured a 37 mm chambering). Another multi-barrel design is the hydraulically driven GAU-8 Avenger 30 mm autocannon, carried on the A-10 Thunderbolt II (Warthog) attack aircraft, a heavily armored close air-support aircraft. It is a seven-barreled cannon designed for tank-killing and is currently the largest bore multi-barrel weapon active in the U.S. arsenal, and heaviest autocannon ever mounted into an aircraft, outweighing the WW II German Bordkanone BK 7,5 75mm aircraft-mount, tank-killing single barrel autocannon by some 630 kg (1,389 lb), with ammunition. The Gryazev-Shipunov GSh-6-23 and GSh-6-30 are Russian gas-powered rotary cannon with maximum cyclic rates of 9,000 to 10,000 rounds per minute. Self-driven examples While electric motors were used to rotate the Vulcan barrels, a few examples of self-operated Gatling-derived weapons use the blow-forward, recoil or gas impulse from their ammunition. The Bangerter machine gun uses a blow-forward operation and is the most complex example. The Slostin machine gun uses a similar operation but with gas pistons on each barrels. The GShG-7.62 machine gun and GSh-6-23, both use a more effective, simpler gas piston drive in the center of the barrel cluster. Minigun Technically not a "cannon", the Minigun is more correctly