page_title: Cannon
section_title: Autocannon
hierarchical_section_title: Cannon / History / 20th and 21st centuries / Autocannon
caption_attribution_description: U.S.S. Vixen, Maxim machine gun and gunner Smith. The gun appears to be a Maxim-Nordenfelt 37-mm 1-pounder autocannon, known to the British as a "pom-pom".
context_page_description: A cannon is a type of gun classified as artillery that launches a projectile using propellant. In the past, gunpowder was the primary propellant before the invention of smokeless powder during the late 19th century. Cannons vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. The word cannon is derived from several languages, in which the original definition can usually be translated as tube, cane, or reed. In the modern era, the term cannon has fallen into decline, replaced by guns or artillery if not a more specific term such as howitzer or mortar, except for high calibre automatic weapons firing bigger rounds than machine guns, called autocannons. The word 'cannon' can be both singular and plural.
  The earliest known depiction of cannon appeared in Song dynasty China as early as the 12th century; however, solid archaeological and documentary evidence of cannon do not appear until the 13th century.
context_section_description: Autocannons have an automatic firing mode, similar to that of a machine gun. They have mechanisms to automatically load their ammunition, and therefore have a higher rate of fire than artillery, often approaching, or, in the case of rotary autocannons, even surpassing the firing rate of a machine gun. While there is no minimum bore for autocannons, they are generally larger than machine guns, typically 20 mm or greater since World War II and are usually capable of using explosive ammunition even if it isn't always used. Machine guns in contrast are usually too small to use explosive ammunition.
  Most nations use rapid-fire cannon on light vehicles, replacing a more powerful, but heavier, tank gun. A typical autocannon is the 25 mm "Bushmaster" chain gun, mounted on the LAV-25 and M2 Bradley armoured vehicles. Autocannons may be capable of a very high rate of fire, but ammunition is heavy and bulky, limiting the amount carried. For this reason, both the 25 mm Bushmaster and the 30 mm RARDEN are deliberately designed with relatively low rates of fire. The typical rate of fire for a modern autocannon ranges from 90 to 1,800 rounds per minute. Systems with multiple barrels, such as a rotary autocannon, can have rates of fire of more than several thousand rounds per minute. The fastest of these is the GSh-6-23, which has a rate of fire of over 10,000 rounds per minute.
  Autocannons are often found in aircraft, where they replaced machine guns and as shipboard anti-aircraft weapons, as they provide greater destructive power than machine guns.
caption: A large bore Maxim on USS Vixen c. 1898
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