20 mm caliber is a specific size of popular

autocannon An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bull ...

ammunition. It is typically used to distinguish smaller-caliber weapons, commonly called "

gun A gun is a ranged weapon designed to use a shooting tube (gun barrel) to launch projectiles. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns/cannons, spray guns for painting or pressure washing, pr ...

s", from larger-caliber "

cannon A cannon is a large- caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder ...

s" (e.g.

machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifles) a ...

vs.

). All 20 mm cartridges have an outside

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...

(

bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. Bullets are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax. Bullets are made in various shapes and co ...

) diameter and

barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...

bore diameter of . These projectiles are typically long, cartridge cases are typically long, and most are shells, with an explosive payload and detonating

fuze In military munitions, a fuze (sometimes fuse) is the part of the device that initiates function. In some applications, such as torpedoes, a fuze may be identified by function as the exploder. The relative complexity of even the earliest fuze d ...

. Weapons using this caliber range from

anti-materiel rifle An anti-materiel rifle (AMR) is a rifle designed for use against military equipment, structures, and other hardware (materiel). Anti-materiel rifles are chambered in significantly larger calibers than conventional rifles and are employed to elimin ...

s and

anti-tank rifles An anti-tank rifle is an anti-materiel rifle designed to penetrate the armor of armored fighting vehicles, most commonly tanks, armored personnel carriers, and infantry fighting vehicles. The term is usually used for weapons that can be carried ...

to aircraft autocannons and

anti-aircraft guns Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...

Usage

Twenty-millimeter-caliber weapons are generally not used to target individual soldiers, but have targets such as vehicles, buildings, or aircraft.

Types of ammunition

High explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

(HE) *

High explosive incendiary In warfare, high-explosive incendiary (HEI) is a type of ammunition specially designed to impart energy and therefore damage to its target in one or both of two ways: via a high-explosive charge and/or via its incendiary (fire-causing) effects. ...

(HEI) *

Armor-piercing Armour-piercing ammunition (AP) is a type of projectile designed to penetrate either body armour or vehicle armour. From the 1860s to 1950s, a major application of armour-piercing projectiles was to defeat the thick armour carried on many warsh ...

(AP) * Semi-armor-piercing high explosive incendiary (SAPHEI) *

Armor-piercing discarding sabot Armour-piercing discarding sabot (APDS) is a type of spin-stabilized kinetic energy projectile for anti-armour warfare. Each projectile consists of a sub-calibre round fitted with a sabot. The combination of a lighter sub-calibre projectile wi ...

(APDS) *High explosive fragmentation tracer (HEF-T) * High explosive high capacity (HE-M) *Penetrator with enhanced lateral effect (PELE) *Target practice - inert projectile (i.e., PGU-27A/B)PGU-27A/B TP/ PGU-28A/B SAPHEI / PGU-30A/B TP-T
/ref> Used for training (TP) *Target practice tracer - inert projectile with tracer material in base for visual trajectory tracking (i.e., PGU-30A/B) (TP-T)

20 mm weapons

Each weapon is listed with its cartridge type appended.

Current weapons

Historical weapons

Cartridge type indicates the diameter of projectile and the length of the cartridge that holds it; for example 20×102mm is a 20 mm projectile in a 102 mm long case. Only rarely do two designers use the same case length, so this designation is usually definitive. Some cartridge types have additional letters or information about them listed. A B following the case length such as the 20X138B, indicates the cartridge has a belt which is used for headspacing. An R indicates a rimmed cartridge such as the 20X145R. An RB indicates a rebated rim, one which is a smaller diameter than the case head such as the Oerlikon 20X110RB.

References

{{Reflist

External links

FAS: 20 mm Cannon AmmunitionATK produced 20, 25 & 30 mm caliber ammunitionRapid Fire: 20 mm Antitank Rifle Cartridges imageRapid Fire: 20 mm Autocannon Cartridges WWII image 1Rapid Fire: 20 mm Autocannon Cartridges WWII image 2Rapid Fire: 20 mm Autocannon Cartridges Post-WWII image
20mm sniper rifles Large-caliber cartridges