Invented by Dr. Richard Jordan Gatling by mid-19th century with the model 1862 Gatling gun, which was adopted by the U.S. Navy, machine guns have been around for a very long time. Around the same period and created by the same man, the modern minigun was made in the 1860s. Dr. Gatling replaced the hand-cranked mechanism of a rifle-caliber Gatling gun with an electric motor, a relatively new invention at the time. Although “minigun” refers to a specific model of weapon that General Electric originally produced, the term “minigun” has come to refer to any externally powered Gatling gun of rifle caliber.
The modern minigun features Gatling-style rotating barrels with an external power source, normally an electric motor. The “mini” in the name is in comparison to designs that use a similar firing mechanism but larger shells, such as 20-millimeter M61 Vulcan, and “gun” for a caliber size smaller than that of a cannon, typically 20-mm and higher. This video shows the effectiveness of the mini gun compared to the machine gun. Truly awesome.