Autocannon

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An autocannon is a projectile weapon with a larger caliber (calibre) than a machine gun (i.e., usually 20mm or greater), but smaller than a field gun or other artillery. They have mechanisms to automatically load the ammunition and have a faster rate of fire than artillery.

Contents 1 History 2 In fiction 3 See also 4 References

[edit] History

The first known autocannon in a primitive form was invented in the 16th century by Fathullah Shirazi, a Persian-Indian polymath and mechanical engineer, who worked for Akbar the Great in the Mughal Empire. As opposed to the polybolos and repeating crossbows used earlier in ancient Greece and China, respectively, Shirazi's rapid-firing machine had multiple gun barrels that fired hand cannon.^[1]

Some of the first modern autocannon were heavy versions of the Maxim gun known as "pom-poms". In the First World War these fired a 1 pound shell of about 37 mm calibre.

The term cannon was used during World War II to describe guns used in aircraft, where the distinction was that the shells were explosive, as opposed to the solid shot used in machine gun bullets. Solid-shot projectiles are used by machine guns and other small arms for calibers up to 15mm. At 20mm caliber, explosive shells are large enough to produce a significant amount of effective fragmentation, e.g., fragments of a suitable size and velocity to either incapacitate or kill a human.^[2] After the war similar guns were used with non-explosive rounds in the anti-tank role, and the name autocannon started to become popular. Autocannon today are typically distinguished by their incorporation of some method of automated loading and firing.

Examples of autocannon are the 25 mm M242 Bushmaster mounted on the M2/M3 Bradley, the Bofors 40mm anti-aircraft gun, the Mauser BK-27, which is used in all aircraft and on many navy vessels of the Bundeswehr and also by the US Navy and the 30mm GAU-8 used in the A-10 Warthog.

Shells used in autocannon include high explosive dual purpose with incendiary and tracer variants, frangible, armor piercing (AP), high velocity armor piercing (HVAP), armor piercing discarding sabot (APDS), and armor piercing fin stabilized discarding sabot (APFSDS). HVAP, APDS, and later, APFSDS, were developed subsequent to the first AP rounds and represent improved armor penetration capability.

World War II saw the first widespread use of autocannon, although the weapons of that era were neither termed as such nor purpose-built for engaging ground targets.^[3] Deployment of autocannon in aircraft was common to practically all the combatants, as was their use as land-based and shipboard anti-aircraft guns. Use of autocannon by ground forces against ground targets was not as common, although both the German Wehrmacht and the late-war French Army often used automatic anti-aircraft guns ranging in bore size from 20mm to 40mm in ground combat.^[4] Rarely, larger automatic guns were used, such as the Molins gun. Postwar, both the western powers and the Soviet Union increasingly adopted autocannon for a wide variety of roles in air, naval, and ground warfare.

Modern tank guns (around 120 mm) have been fitted with automatic loading systems (typically Soviet Union and Russian main battle tanks, along with French, have used these for reasons of space) and although they technically might be considered to be autocannon they are not referred to as such, due to their relatively low rate of fire. A notable exception to this might be the Russian AK-130 130mm/70 twin naval gun, used on most large Russian warships, which has a fire rate in excess of 60 rounds per minute, currently the fastest-firing weapon in excess of 120 mm known.

Although capable of generating a high volume of fire, autocannon are limited by the amount of ammunition that can be carried by the weapons systems mounting them. For this reason, both the U.S. 25mm Bushmaster and the British 30mm Rarden are deliberately designed with relatively slow rates of fire in order to extend the amount of time they can be employed on a battlefield before requiring a resupply of ammunition. The rate of fire of modern autocannon ranges from 90 rounds per minute (British RARDEN) to 1,800 rounds per minute (Mauser BK-27). Systems with multiple barrels can have rates of fire of several thousand rounds per minute.^[5] Such extremely high rates of fire are effectively employed by aircraft in air-to-ground and air-to-air combat, where the target dwell time is short and weapons are typically operated in brief bursts.

[edit] In fiction

There have been a plethora of weapons described as autocannon in various science-fiction universes. In Warhammer 40,000, an autocannon refers to a particular class of heavy repeating cannon that are capable of dealing with heavy infantry armour (such as Tau, Kasrkin and Scout Marines.) It also has the ability to take out all but the heaviest armoured vehicles. It fulfills most of the roles as a modern day autocannon, as both a heavy infantry weapon and light to medium tank armament. ^[6] In the Battletech universe, autocannon are large-caliber repeating projectile weapons mounted on battlemechs and other vehicles. There are several types of autocannon in Battletech, such as higher-rate-of-fire "ultra autocannon", the shotgun-like "LB-X" autocannon, and the gatling-style "Rotary" autocannon.^[7]

[edit] See also

• Revolver cannon

[edit] References

• Department of the Army. Ballistic Data Performance of Ammunition, TM 9-1907. Washington, D.C.: Government Printing Office, 1948.
• Williams, Anthony G. Rapid Fire. Shrewsbury: Airlife Publishing Ltd., 2000. ISBN 1-84037-435-7.