Gatling guns have been the first firearms with a firing rate close to modern machine guns. Their principle is easy: A set of rotating barrels is turned by cranking a wheel, with one barrel after the other firing a round when it is in shooting position. This makes them technically and legally a repeating gun, not a full auto one – but it is close enough.
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http://www.youtube.com/watch?v=qxtHtPK2MH8
Retrieved Monday 24th October 2011 2:00 pm EDT