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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. One of the main differences between different machine gun models is the loading mechanism. The early manual machine guns, such as the Gatling gun, used a device called the ammunition hopper.
Hoppers are just metal boxes containing loose individual cartridges that fit on top of the machine gun mechanism. One by one, the cartridges fall out of the hopper and into the breech. Hoppers can hold a good amount of ammunition and they're easy to reload even while the gun is firing, but they are fairly cumbersome and only work if the gun is positioned right side up.
The hopper system was replaced by the belt-fed system , which helps control the ammunition's movement into the gun. Ammunition is contained on a long belt, which the operator holds, or is contained in a bag or box.
After a round is fired, it moves out of the way, and a new round slips into place. Another system is the spring-operated magazine. In this system, a spring pushes cartridges in a magazine casing up into the breech. The main advantages of this mechanism are that it's reliable, lightweight and easy to use. The main disadvantage is that it can only hold a relatively small amount of ammunition. Heavy belt-fed machine guns, usually mounted on a tripod or a vehicle, may need more than one operator.
Individual troops usually carry light weapons, with extendible bipods or tripods for stability. Smaller automatic guns that use cartridge magazines are classified as automatic rifles, assault rifles or submachine guns. In a general sense, the term "machine gun" describes all automatic weapons, including these smaller weapons, but it's also used to describe heavy belt-fed guns specifically. For sheer volume of ammunition, the belt system is usually the best option.
Ammunition belts consist of a long string of cartridges fastened together with pieces of canvas or, more often, attached by small metal links. Guns that use this sort of ammo have a feed mechanism driven by the recoil motion of the bolt.
The bolt 1 in this gun has a small cam roller 5 on top of it. As the bolt moves, the cam roller slides back and forth in a long, grooved feed cam piece 2. When the cam roller slides forward, it pushes the feed cam to the right against a return spring 6. When the cam roller slides backward, the spring pushes the cam back to the left. The feed cam lever is attached to a spring-loaded pawl 8 , a curved gripper that rests on top of the ammunition belt.
As the cam and lever move, the pawl moves out, grabs onto a cartridge and pulls the belt through the gun. When the bolt moves forward, it pushes the next cartridge into the chamber.
The feed system drives the ammunition belt through cartridge guides 2 just above the breech. As the bolt slides forward, the top of it pushes on the next cartridge in line.
This drives the cartridge out of the belt, against the chambering ramp 3. The chambering ramp forces the cartridge down in front of the bolt. The bolt has a small extractor, which grips the base of the cartridge shell when the cartridge slides into place. As the cartridge slides in front of the bolt, it depresses the spring-loaded ejector 6.
When the firing pin hits the primer, propelling the bullet down the barrel, the explosive force drives the operating rod and attached bolt backward. When the shell clears the chamber wall, the ejector springs forward, popping the shell out of the gun through the ejection port. This system lets you fire continuously without reloading. The basic mechanism of the machine gun has remained the same for more than a hundred years, but gun manufacturers are continually adding new modifications.
One modern design transforms from a box to a gun with the single push of a button [source: Sofge]. In addition, new lightweight small arms technologies LSAT are made of lighter materials that could reduce the weight of machine guns and their ammunition by 40 percent. Whether or not you've ever held a machine gun or even seen one, this powerful device has had a profound effect on your life.
Machine guns have had a hand in dissolving nations, repressing revolutions, overthrowing governments and ending wars. In no uncertain terms, the machine gun is one of the most important military developments in the history of man. For additional information about machine guns and related topics, head to the links on the following page. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.
Mobile Newsletter chat subscribe. How Machine Guns Work. Machine guns changed warfare forever, but they run on basic concepts. See more gun pictures. Ballistic Background: Barrel " ". Medium machine guns such as this one are an essential element in the modern arsenal. Photo courtesy Department of Defense. The First Guns " ". A percussion cap gun left and a flintlock gun right , two important steps on the way to modern firearms. Revolvers Click on the trigger to see how a revolver fires.
Initially, the trigger lever pushes the hammer backward.
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