20 mm caliber is a specific size of popular autocannon ammunition. The dividing line between smaller-caliber weapons, commonly called "guns", from larger-caliber "cannons" (e.g. machine gun vs. autocannon), is conventionally taken to be the 20 mm round, the smallest caliber of autocannon. All 20 mm cartridges have an outside projectile (bullet) diameter and barrel bore diameter of approximately 0.787 inches (20.0 mm). These projectiles are typically 75 to 127 mm (3–5 in) long, cartridge cases are typically 75 to 152 mm (3–6 in) long, and most are shells, with an explosive payload and detonating fuze.
Weapons using this caliber range from anti-materiel rifles and anti-tank rifles to aircraft autocannons and anti-aircraft guns.
Usage
Twenty millimeter caliber weapons are generally not used to target individual soldiers, but rather objects such as vehicles, buildings, or aircraft.
Types of ammunition
- High explosive (HE)
- High explosive incendiary (HEI)
- Armor-piercing (AP)
- Semi-armor-piercing high explosive incendiary (SAPHEI)
- Armour-piercing discarding sabot (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)[1] 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
Weapon | Country of origin | Cartridge | Notes |
---|---|---|---|
Neopup PAW-20 | ![]() |
20×42 mm | |
Denel NTW-20 | ![]() |
20×82 mm Mauser | |
Denel Vektor GA-1 | ![]() |
||
Vidhwansak | ![]() |
||
Anzio 20mm rifle | ![]() |
20×102 mm | |
Arash anti-materiel rifle | ![]() |
||
M61 Vulcan | ![]() |
||
M197 electric cannon | ![]() |
||
M39 cannon | ![]() |
||
GIAT M621 | ![]() |
||
ZVI PL-20 Plamen | ![]() |
||
Nexter Narwhal 20A | ![]() |
Based on the M621 | |
Şahi 20-102 | ![]() |
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XM301 | ![]() |
[2] | |
Denel NTW-20 | ![]() |
20×110 mm Hispano | |
Metallic RT-20 | ![]() |
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Truvelo CMS 20x110mm | ![]() |
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Yugoimport-SDPR M71/08 | ![]() |
Single barrel development of Zastava M55 | |
Oerlikon KAE (KAA/KAB) | ![]() |
20×128 mm | Formerly known as Oerlikon 204GK/5TG |
Meroka CIWS | ![]() |
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Oerlikon KAD | ![]() |
20×139 mm | Formerly known as Hispano-Suiza HS.820 |
GIAT M693/20 mm modèle F2 | ![]() |
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Rheinmetall Rh 202 | ![]() |
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Denel Land Systems GI-2 | ![]() |
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Nexter Narwhal 20B | ![]() |
Based on the 20 mm F2 |
Historical weapons
Naming conventions
The usual nomenclature of ammunition indicates the diameter of projectile and the length of the cartridge that holds it; for example, 20×102 mm is a 20 mm projectile in a 102 mm long case.
Though this designation is often assumed to be unique, this is not always the case, e.g. there are three different 20×110 mm types which are not compatible. These may be distinguished in that some cartridge designations may include additional letters or names as a suffix, e.g. the various different types of 20×110 mm might be distinguished as 20×110 mm Hispano, 20×110 mm RB and 20×110 mm USN.
Common suffixes
- B e.g. 20×138B: the cartridge has a belt which is used for headspacing, i.e. it helps ensure the correct positioning within the gun's chamber.
- R e.g. 20×145R: a rimmed cartridge: the diameter of the rim forming the base is larger than that of the cartridge case itself.
- RB e.g. Oerlikon 20×110RB: rebated rim, one where the rim is a smaller diameter than the case head allowing the extractor to follow it into the chamber, facilitating advanced-primer ignition, a recoil-moderating system.
See also
References
- ^ PGU-27A/B TP/ PGU-28A/B SAPHEI / PGU-30A/B TP-T
- ^ "Otomatik Orta Kalibre Top". 17 October 2022. Retrieved 17 October 2022.
- ^ Williams, Anthony G (January 4, 2021). "Ammunition Data Tables - 20 mm Calibre Cartridges". Military Guns & Ammunition. Solo Publications. Archived from the original on March 30, 2022. Retrieved April 17, 2022.
External links
- FAS: 20 mm Cannon Ammunition
- ATK produced 20, 25 & 30 mm caliber ammunition
- Rapid Fire: 20 mm Cartridge Data Table
- Rapid Fire: 20 mm Antitank Rifle Cartridges image
- Rapid Fire: 20 mm Autocannon Cartridges WWII image 1
- Rapid Fire: 20 mm Autocannon Cartridges WWII image 2
- Rapid Fire: 20 mm Autocannon Cartridges Post-WWII image