Machine gun

A machine gun is a fully automatic firearm that is capable of firing bullets in rapid succession. Such automatic weapons with a caliber of 20 mm or larger are generally referred to as autocannons.

Components

All machine guns require the following components:

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• A feed system to load the firing chamber. Cartridges can be fed into the chamber by a variety of methods, the most common being spring-fed magazines or ammunition belts.
• A trigger mechanism to fire the round. This includes the actual trigger, a trigger sear to catch the bolt, a bolt and a firing pin, as well as other components. Typically, the act of pulling the trigger causes something to strike the primer on the round in the chamber and disengages the sears. This allows continual cycling of the bolt until the trigger is released. A sear then grabs the bolt or firing pin. This stops the machine gun at some point in its cycle.
• An extractor system to eject the spent or misfired cartridge. Usually this is fairly simple. A pin on the side of the bolt catches a ridge on the cartridge and flicks it out an ejection port.

These components form a mechanism which must be powered by something. If powered by a spring absorbing the recoil of a fired cartridge, it is called recoil operated. If powered by the expanding gases of a fired cartridge, it is called gas actuated. If it powered by an external force, such as a motor, it is usually called a chain gun.

Related Topics:
Recoil - Gas actuated - Chain gun

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