How does Machine Gun works....?

By:Prayag Nao

Machine Guns and Gun Systems



In the 1800s, gun manufacturers designed a number of mechanisms to address the problems associated with limited firing ability. A lot of these early machine guns combined several barrels and firing hammers into a single unit. Among the most popular designs was the Gatling gun, named after its inventor Richard Jordan Gatling.
This weapon -- the first machine gun to gain widespread popularity -- consists of six to 10 gun barrels positioned in a cylinder. Each barrel has its own breech and firing pin system. To operate the gun, you turn a crank, which revolves the barrels inside the cylinder. Each barrel passes under an ammunition hopper, or carousel magazine, as it reaches the top of the cylinder. A new cartridge falls into the breech and the barrel is loaded.
Each firing pin has a small cam head that catches hold of a slanted groove in the gun's body. As each barrel revolves around the cylinder, the groove pulls the pin backward, pushing in on a tight spring. Just after a new cartridge is loaded into the breech, the firing-pin cam slides out of the groove and the spring propels it forward. The pin hits the cartridge, firing the bullet down the barrel. When each barrel revolves around to the bottom of the cylinder, the spent cartridge shell falls out of an ejection port.
The Gatling gun played an important role in several 19th century battles, but it wasn't until the early 20th century that the machine gun really established itself as a weapon to be reckoned with.
The Gatling gun is often considered a machine gun because it shoots a large number of bullets in a short amount of time. But unlike modern machine guns, it isn't fully automatic: You have to keep cranking if you want to keep shooting. The first fully automatic machine gun is actually credited to an American named Hiram Maxim. Maxim's remarkable gun could shoot more than 500 rounds per minute, giving it the firepower of about 100 rifles.
The basic idea behind Maxim's gun, as well as the hundreds of machine gun designs that followed, was to use the power of the cartridge explosion to reload and re-cock the gun after each shot. There are three basic mechanisms for harnessing this power:
  • Recoil systems
  • Blowback systems
  • Gas mechanisms

Machine Gun Recoil Systems



Click and hold the trigger to see how a recoil-action gun fires. For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms.

The first automatic machine guns had recoil-based systems. When you propel a bullet down the barrel, the forward force of the bullet has an opposite force that pushes the gun backward. In a gun built like a revolver, this recoil force just pushes the gun back at the shooter. But in a recoil-based machine gun, moving mechanisms inside the gun absorb some of this recoil force.
Here's the process: To prepare this gun to fire, you pull the breech bolt (1) back, so it pushes in the rear spring (2). The trigger sear (3) catches onto the bolt and holds it in place. The feed system runs an ammunition belt through the gun, loading a cartridge into the breech (more on this later). When you pull the trigger, it releases the bolt, and the spring drives the bolt forward. The bolt pushes the cartridge from the breech into the chamber. The impact of the bolt firing pin on the cartridge ignites the primer, which explodes the propellant, which drives the bullet down the barrel.
The barrel and the bolt have a locking mechanism that fastens them together on impact. In this gun, both the bolt and the barrel can move freely in the gun housing. The force of the moving bullet applies an opposite force on the barrel, pushing it and the bolt backward. As the bolt and barrel slide backward, they move past a metal piece that unlocks them. When the pieces separate, the barrel spring (4) pushes the barrel forward, while the bolt keeps moving backward.
The bolt is connected to an extractor, which removes the spent shell from the barrel. In a typical system, the extractor has a small lip that grips onto a narrow rim at the base of the shell. As the bolt recoils, the extractor slides with it, pulling the empty shell backward.
The backward motion of the bolt also activates the ejection system. The ejector's job is to remove the spent shell from the extractor and drive it out of an ejection port.
When the spent shell is extracted, the feeding system can load a new cartridge into the breech. If you keep the trigger depressed, the rear spring will drive the bolt against the new cartridge, starting the whole cycle over again. If you release the trigger, the sear will catch hold of the bolt and keep it from swinging forward.

Machine Gun Blowback Systems



Click and hold the trigger to see how a blowback-action gun fires. 

 For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms. See the "Machine Gun Feeding: Belt System" section to find out how these components work.
A blowback system is something like a recoil system, except that the barrel is fixed in the gun housing, and the barrel and bolt don't lock together. You can see how this mechanism works in the diagram below.
This gun has a sliding bolt (3) held in place by a spring-driven cartridge magazine (5), and a trigger mechanism (1). When you slide the bolt back, the trigger sear (2) holds it in place. When you pull the trigger, the sear releases the bolt, and the spring drives it forward. After the bolt chambers the cartridge, the firing pin sets off the primer, which ignites the propellant.
The explosive gas from the cartridge drives the bullet down the barrel. At the same time, the gas pressure pushes in the opposite direction, forcing the bolt backward. As in the recoil system, an extractor pulls the shell out of the barrel, and the ejector forces it out of the gun. A new cartridge lines up in front of the bolt just before the spring pushes the bolt forward, starting the process all over again. This continues as long as you hold the trigger down and there's ammunition feeding into the system.

Machine Gun Gas Systems



Click and hold the trigger to see how a gas-action gun fires. 

For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms. See the "Machine Gun Feeding: Belt System" section to find out how these components work.
The gas system is similar to the blowback system, but it has some additional pieces. The main addition is a narrow piston attached to the bolt, which slides back and forth in a cylinder positioned above the gun barrel. You can see how this system works in the diagram below.
This gun is basically the same as one using the blowback system, but the rear force of the explosion doesn't propel the bolt backward. Instead, the forward gas pressure pushes the bolt back. When the bolt swings forward to fire a cartridge, it locks onto the barrel. Once the bullet makes its way down the barrel, the expanding gases can bleed into the cylinder above the barrel. This gas pressure pushes the piston backward, moving it along the bottom of the bolt. The sliding piston first unlocks the bolt from the barrel, and then pushes the bolt back so a new cartridge can enter the breech.
The diagrams we've presented only depict particular examples of how these systems work. There are hundreds of machine gun models in existence, each with its own specific firing mechanism. These guns differ in a number of other ways as well. In the next two sections, we'll look at some of the key differences between various machine gun models.

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