The Gatling gun is a machine gun that has many barrels that fire bullets by turning the barrels around in a circle. It was the first machine gun ever made. It was first used by the Union Army during the American Civil War. Although it was very powerful, it was not much used because it cost a lot of money and was heavy. It was used more often in other wars during the second half of the 19th century. It was used in the Anglo-Zulu War, the Boshin War, and the Spanish-American War. Early in the 20th century armies stopped using it because other machine guns were better.
The Minigun is based on the Gatling gun. The Gatling gun is a machine gun, but it is not called an automatic weapon because a user must continue to crank it instead of merely holding down the trigger. Still it was very useful in the wars.