David Marker, age 13, of Casper, Wyo., for his question:
WHEN WAS THE MACHINE GUN INVENTED?
A machine gun is an automatic weapon that is able to deliver a rapid and continuous fire of bullets as long as the trigger is pressed. A type of machine gun appeared as early as the 1500s. It consisted of several guns bound together in a bundle or spread out in a row. A device that was fitted to the gun barrels caused them to fire simultaneously or in series.
But little military success was achieved with early machine guns.
Many quick fire guns appeared at the time of the Civil War. Practical, rapid fire, mechanical guns were also used in the Franco Prussian War, when soldiers operated them with cranks or levers. The French Montigny Mitrailleuse and the American Gatling were among the more successful of these early guns.
In 1889, American born inventor Hiram Maxim developed the first entirely automatic weapon to gain wide acceptance.
By World War I, many different types of machine guns had come into use.
An automatic machine gun can fire from 400 to 1,600 rounds of ammunition each minute. Barrels of machine guns can range in size from .22 caliber to 30 millimeters.
Ammunition is fed into the gun from a cloth or metal belt, or from a cartridge holder called a magazine. Because machine guns fire so rapidly, they must be cooled by water or air. Most machine guns are heavy weapons and are usually mounted on supports.
In all of today's military machine guns, extremely high gas pressure provides the operating energy for the firing cycle. The cycle begins when the propellant charge in the cartridge case burns. This combustion creates the gas pressure that is used in the blowback, gas and recoil operating systems. All three systems fire the projectile through the bore of the barrel, eject the cartridge case, place a new cartridge in the firing chamber and ready the mechanism to repeat the cycle.
The standard United States Army submachine gun is the .45 caliber M 3, a short range weapon that weighs only nine pounds.
By the close of World War I, several types of machine guns were mounted on airplanes. During World War II, fighters and bombers carried machine guns as armament. They also carried automatic cannons up to 20 millimeters in size.
Today, most fighter planes carry rockets for air to air and air to ground use. Bombers use machine guns mounted in groups of two to four in power driven turrets. The Vulcan 20 millimeter aircraft cannon has six rotating barrels. It can fire more than a ton of metal and explosives each minute.
The .60 caliber Browning machine gun was used as an antiaircraft weapon during World War II. It was used alone, or in groups of two to four.
Large caliber automatic cannon that fired explosive shells were also developed as antiaircraft weapons.