The past hundred years have seen numerous important technologies but, perhaps, none as important as machine guns. The invention of machine guns changed forever the way war was conducted and its ruthless application was felt most severely during the two World Wars. They continued to dominate later wars and have made even more rapid progress since then. The machine guns enabled the soldiers to fire hundreds of bullets per minute and were capable of destroying entire platoons in just a matter of a few passes. Machine guns gave rise to different genres of war equipment like tanks just to enable the army to withstand the fusillade of bullets from machine guns.
Amongst the more popular machine guns was the Gatling gun in the 1800s. Manufacturers were grappling to tackle the problem of limited firing capability and had devised a number of mechanisms to address this problem. The Gatling gun comprised of six to ten gun barrels, each with its own breech and firing pin and which were placed in a cylinder. A crank was turned to revolve the barrels and each barrel went through a carousel magazine before reaching the top of the cylinder. The breech was filled with a new cartridge thus loading the barrel. As the barrel got loaded with the new cartridge, the old one would be hit by the pin firing the bullet down the barrel. The used cartridge would be ejected out of an ejection port. In the nineteenth century the Gatling gun was most commonly used and is considered the first among machine guns because of the number of bullets it could shoot in a short time. But, it was still not fully automatic as the crank had to be worked to keep shooting.
It was only in the early twentieth century that guns became fully automatic when an American named Hiram Maxim invented a gun which could shoot more than 500 rounds of bullets per minute doing the work of about 100 rifles at one go. Basically the idea behind this gun and the subsequent guns was to utilize the power of the cartridge explosion to re-load the gun and to re-lock it after each shot and this was done by the recoil system or the blowback system or gas mechanisms.
The recoil mechanism was used in the first automatic machine gun. It was based on the simple principle of every action having an equal and opposite reaction. When a bullet was pushed down the barrel, the bullet moved forward and this force had an opposite force which pushed the gun backward. Unlike in revolvers where the gun simply got pushed back at the shooter, in machine guns mechanisms which were moving inside the gun absorbed some of this force. The spent cartridge was extracted and a new cartridge got loaded into the breech. If the trigger remained depressed, the spring at the back would push the bolt against the new cartridge and the process would start again. If the trigger was released, the sear would hold the bolt to keep it from swinging forward.
The blowback system though similar to the recoil system was different from it in that the barrel was fixed in the gun housing and the bolt and the barrel did not lock together. The bullet was pushed down the barrel by the explosive gas from the cartridge and simultaneously the gas explosion would push in the opposite direction to force the bolt backward. The spent shell would get extracted and would be forced out of the gun by the ejector. A new cartridge would replace the old one and the whole process would begin again. This would continue as long as the trigger was held down and ammunition was kept being fed in the gun.
The gas mechanism was similar to the blowback system with a few extras. The main additional feature was the piston which was attached to the bolt and which would slide back and forth in a cylinder placed above the gun barrel. Unlike in the blowback system the force from behind would not push the bolt back but the forward gas pressure pushed the bolt back. Then when the bolt would swing open to fire the bullet it would get locked onto the barrel. The job of the piston was to unlock the bolt from the barrel and then push it back to facilitate the entry of a new cartridge.
These three systems were the basis of the functioning of the machine guns and there are many machine guns each with its own specific firing systems. The loading mechanism is one of the key differences between various types of machine guns. One of the more popular types of loading mechanism is the spring-operated magazine in which a spring nudges the cartridges in a magazine into the breech. The spring magazine is dependable, easy to operate and lightweight. But, it can only hold a small amount of ammunition.
Another popular system is the hopper system which is quite similar to the Gatling gun system. Hoppers are merely metal boxes which fit into the top of the machine gun and cartridges fall out of the hopper into the breech one by one. Hoppers can hold a fairly large amount of ammunition and are easy to load but they can still get quite cumbersome.
The belt system holds the maximum amount of ammunition and is considered the best. This comprises of a long belt of cartridges held together either by pieces of canvas or by small links of metal. This system allows keeping up continuous firing without reloading.
Machine guns which have heavy belts are usually mounted on tripods or tanks, jeeps, helicopters or any other vehicles and may need more than one operator. One of the popular machine guns in World War I and II was the Vickers MKI which was a belt-fed machine gun.
Machine guns are capable of utter destruction yet they form a vital part of the national security of any nation.