Machine Gun

A machine gun is a fully-automatic mounted or portable firearm, usually designed to fire rifle cartridges in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute.

In United States law, machine gun is a term of art for any fully-automatic firearm.

Overview
The Machine Gun of today has its origins in the 'Volley Gun', originally appearing in the 15th Century. Although they were not 'true' machine guns, in that they did not fire automatically, the general concept was a rapid-fire weapon. The Volley Gun was more or less a single weapon firing shot from multiple single-shot barrels. The original, called a ribauldequin or "organ gun", first designed by Leonardo Da Vinci, was first used during the Hundred Years War by English forces against French soldiers. The weapon was a simple device, consisting of a series of cannons lined inside of a wooden carriage. Another weapon, the Belgian-designed mitrailleuse, was used by French forces during the Franco-Persian war. This was a number of rifled barrels clustered inside of a can-like carriage.

These two weapons, while pioneering the semi-automatic and automatic weapon concepts, were both considered unwieldy and ineffective. They were heavy, and were required to be carried around on carriages drawn by horses. Because of this, they was as immobile and hard to aim as a standard cannon of the age. They were also inaccurate and difficult to load. These weapons were often less effective than a standard cannon loaded with grapeshot.

The first true Machine Guns were the Gatling Guns. These weapons, designed by American designer Dr. Richard Gatling, were carriage-mounted weapons that fired from multiple barrels with individual firing pins. The gun fired black-powder cartridge rounds from a top-loaded hopper system. The original Gatling Guns were fired by rotating a hand-crank, which would feed individual rounds into each of the barrels. As a barrel fired, it would be ejected with the next rotation and cooled slightly. After that, the next barrel would be fed a round and fired. The rate of fire was typically determined by how quickly the crank was rotated. The first use of the Gatling Gun was during the American Civil War, and later used to great effect during the Spanish-American war, by U.S Forces against the Spanish and Cubans, notably during the Battle of San-Juan hill.

A further revolution was made by Austrian Inventor Hiram Maxim. The first recoil-operated Machine Gun, the Maxim Gun, was first introduced in June/July 1883. The gun was the first automatically-fed machine gun, using a recoil-operated system to feed rifle-cartridges on a linked-belt. The concept of using bullet energy would be the concept driving most Semi and Fully Automatic weaponry.

Another system, the gas-operation system, was first used by the Colt-Browning M1895. This weapon used the gases of the fired cartridge to feed rounds in a similar belt-fed system to the Maxim design.

These two systems were major operating systems used by machine guns to today, as well as other weapon systems such as Semi-Automatic rifles and pistols and Assault Rifles.

One of the most prolific uses of these machine guns was during WW1. The machine gun was one of the most iconic weapons of the conflict and was much hated by the troops that had to face them. Their performance in the war, where a single machine gun crew could be the cause of hundreds, maybe thousands, of enemy casualties, was successful enough that many later armies would consider the machine gun their primary weapon. One of the most famous examples of which were the German Armed Forces of Nazi Germany, who considered the MG34 and MG42 machine guns the main weapons of any infantry squad. Machine guns would also later be adopted to two other important weapons of the First World War: The Aeroplane and the Tank.

WW2 saw the introduction of light-machine guns, weapons that while still requiring a tripod or bi-pod system were more portable than the heavy and cumbersome mounted-weapons. It also saw the introduction of the automatic cannon into combat, used by Planes, Anti-Aircraft mounts and armored vehicles.

Machine guns continue to be used into the modern age, in a variety of roles and calibers. From man-portable light-machine guns like the M249 and M60 to mounted, electric driven Gatling Guns like the M134 and even automatic grenade launchers like the Mk. 19. Machine Guns and automatic cannons are also mounted weapons on aircraft, armored vehicles and ships.

Tactics
Generally, the gunners job is to provide their teammates covering and/or suppressing fire. For this, an M60E4 or RPD is better suited for these tasks with their higher damage meaning more risk to being hit once or twice, although all LMGs can do these tasks; all machine gunners tend to have a preference, and the choice can only be truly made through usage of the gun, as with most weapons. A machine gun is also effective against helicopters (this applicable to Call of Duty 4: Modern Warfare only); the two aforementioned LMGs can take out a helicopter in just under one belt of ammo.

The M249 in Call of Duty 4, and in Modern Warfare 2 the MG4, which is a direct competitor to the M249 and its original FN Minimi form, are used most often in the automatic rifle role, which is one of moving support, combining the methods of covering and suppressing fire with accurate aimed fire on visible targets, as one would with a rifle. The extremely high accuracy and low recoil of these weapons is what makes them useful for run and gun role. These guns can easily be used to provide practically any kind of support.