RIFLE & GUN PARTS

Historically, rifles only fired a single projectile with each squeeze of the trigger. Modern rifles are commonly classified as single-shot, bolt-action, semi-automatic, or automatic. Single-shot, bolt-action, and semi-automatic rifles are limited by their designs to fire a single shot for each trigger pull. Only automatic rifles are capable of firing more than one round per trigger squeeze; however, some automatic rifles are limited to fixed bursts of two, three, or more rounds per squeeze.

Modern automatic rifles overlap to some extent in design and function with machine guns. In fact, many light machine guns are adaptations of existing automatic rifle designs, such as the RPK and M27 Infantry Automatic Rifle. A military's light machine guns are typically chambered for the same caliber ammunition as its service rifles. Generally, the difference between an automatic rifle and a machine gun comes down to weight, cooling system, and ammunition feed system. Rifles, with their relatively lighter components (which overheat quickly) and smaller capacity magazines, are incapable of sustained automatic fire in the way that machine guns are; they trade this capability in favor of increased mobility. Modern military rifles are fed by magazines, while machine guns are generally belt-fed. Many machine guns allow the operator to quickly exchange barrels in order to prevent overheating, whereas rifles generally do not. Most machine guns fire from an open bolt in order to reduce the danger of "cook-off", while almost all rifles fire from a closed bolt for accuracy. Machine guns are often crewed by more than one soldier; the rifle is an individual weapon