Autocannon
Due to the heavy weight and recoil, they are typically installed on fixed mounts, wheeled carriages, ground combat vehicles, aircraft, or watercraft, and are almost always crew-served, or even remote-operated with automatic target recognition/acquisition (e.g. sentry guns and naval CIWS).
Common types of ammunition, among a wide variety, include HEIAP, HEDP and more specialised armour-piercing (AP) munitions, mainly composite rigid (APCR) and discarding sabot (APDS) rounds.
Capable of generating extremely rapid firepower, autocannons overheat quickly if used for sustained fire, and are limited by the amount of ammunition that can be carried by the weapons systems mounting them.
The pom-pom fired 1 pound (0.45 kg) gunpowder-filled explosive shells at a rate of over 200 rounds a minute: much faster than conventional artillery while possessing a much longer range and more firepower than the infantry rifle.
Larger examples, such as the 40 mm Vickers S, were mounted in ground attack aircraft to serve as an anti-tank weapon, a role to which they were suited as tank armour is often lightest on top.
During the inter-war years, aircraft underwent extensive evolution and the all-metal monoplane, pioneered as far back as the end of 1915, almost entirely replaced wood and fabric biplanes.
When the Second World War did break out, it was swiftly realised that the power of contemporary aircraft allowed armour plate to be fitted to protect the pilot and other vulnerable areas.
These new defenses, synergistically with the general robustness of new aircraft designs and of course their sheer speed, which made simply shooting them accurately in the first place far more difficult, entailed that it took a lot of such bullets and a fair amount of luck to cause them critical damage; but potentially a single cannon shell with a high-explosive payload could instantly sever essential structural elements, penetrate armour or open up a fuel tank beyond the capacity of self-sealing compounds to counter, even from fairly long range.
Thus by the end of the war, the fighter aircraft of almost all the belligerents mounted cannon of some sort, the only exception being the United States which in most cases favoured the Browning AN/M2 "light-barrel" .50 calibre heavy machine gun.
Continued ineffectiveness against aircraft despite the large numbers installed during the second World War led, in the West, to the removal of almost all shipboard anti-aircraft weapons in the early post-war period.
The German Luftwaffe deployed small numbers of the experimental Bordkanone series of heavy aircraft cannon in 37, 50 and 75 mm calibres, mounted in gun pods under the fuselage or wings.
The 37 mm BK 3,7 cannon, based on the German Army's 3.7 cm FlaK 43 anti-aircraft autocannon was mounted in pairs in underwing gun pods on a small number of specialized Stuka Panzerknacker (tank buster) aircraft.
The PaK 40 semi-automatic 7.5 cm calibre anti-tank gun was the basis for the BK 7,5 in the Junkers Ju 88 P-1 heavy fighter and Henschel Hs 129 B-3 twin engined ground attack aircraft.
