Autocannons

An autocannon is a rapid-fire firearm that fires explosive or armor-piercing shells in larger calibers than typical small-arms weapons. Autocannons are designed to be loaded and fired automatically, using belt- or drum-feed ammunition and mechanical, hydraulic, or electric drives to cycle rounds. They are used on a variety of platforms where a high rate of fire and substantial missiles are needed, including aircraft, naval vessels, and armored ground vehicles. Calibers commonly range from about 20 mm to 40 mm, with larger and smaller variants developed for specialized roles.

Design and operation center on delivering a high sustained rate of fire while managing recoil, barrel wear, and ammunition consumption. Most autocannons employ gas-operated or recoil-operated mechanisms, often with external power sources or recoil-managed designs to improve control. They typically use belts or magazines and require cooling systems to prevent overheating during extended firing. The choice of ammunition—high-explosive, armor-piercing, canister, or programmable rounds—depends on the intended target, such as aircraft, light armor, or soft targets.

Applications vary by platform. Aircraft-mounted autocannons provide close-range fire support and air defense; naval autocannons perform shipboard air and surface defense; and armored or armored-support vehicles use autocannons to engage targets at intermediate ranges with substantial firepower. Notable examples include the 30 mm GAU-8 Avenger, the 20 mm M61 Vulcan, and the 35 mm Oerlikon Millennium; historical systems include various 40 mm, 76 mm, and 100 mm autocannons used on ships and land installations. Autocannons are distinguished from smaller machine guns by their larger calibers and explosive ammunition, offering increased lethality at longer ranges but with greater weight and complexity.