Automatic firearm

How it works

At each shot an automatic firearm performs several steps automatically: the fired cartridge is extracted from the cartridge case, ejected, and the mechanism loads a fresh round into the chamber. Ammunition is typically supplied from a detachable box or drum magazine or from a linked belt. The energy to operate these steps may come from gas tapped from the barrel, direct recoil, or a simple blowback action.

Common mechanisms and features

• Gas-operated: uses expanding propellant gas to drive an operating rod or piston.
• Recoil-operated: uses the rearward motion of barrel and bolt after firing.
• Blowback: relies on case and breech energy with fewer moving parts.
• Bolt behavior: designs may fire from an open bolt or closed bolt, affecting cooling and accuracy.
• Select-fire and burst modes: many military weapons allow switching between semi-automatic, fully automatic, or limited burst settings.

History and development

Automatic firing systems emerged in the late 19th and early 20th centuries with purpose-built machine guns for military use. Advances in metallurgy, ammunition, and operating systems led to smaller, lighter designs such as submachine guns and assault rifles, while larger belt-fed machine guns remain standard for sustained fire roles.

Uses, distinctions and considerations

Automatic firearms are primarily military and law-enforcement tools where sustained fire or suppressive capability is required. For civilians, ownership and use are regulated in many countries. Important distinctions include the difference between automatic and semi-automatic operation, as well as practical trade-offs: automatic fire increases ammunition consumption, heat, and wear, and usually reduces practical accuracy for aimed fire.

For technical diagrams, legal summaries, or further reading, see linked resources: magazine and feeding, cartridge extraction, chamber and headspace.