Wikipedia

20 mm caliber

(Redirected from 20mm)
"20mm" redirects here. For the model scale, see List of scale model sizes.

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

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A 20×102 mm round (second from left) with .50 BMG rounds, golf ball, and a stick of 168-pin SDRAM computer memory

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

Types of ammunition

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20 mm weapons

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Each weapon is listed with its cartridge type appended.

Current weapons

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Weapon Country of origin Cartridge Notes
Neopup PAW-20   South Africa 20×42 mm
Denel NTW-20   South Africa 20×82 mm Mauser
Denel Vektor GA-1   South Africa
Vidhwansak   India
Anzio 20mm rifle   United States 20×102 mm
Arash anti-materiel rifle   Iran
M61 Vulcan   United States
M197 electric cannon   United States
M39 cannon   United States
GIAT M621   France
ZVI PL-20 Plamen   Czech Republic
Nexter Narwhal 20A   France Based on the M621
Şahi 20-102   Turkey [2]
XM301   United States
Denel NTW-20   South Africa 20×110 mm Hispano
Metallic RT-20   Croatia
Truvelo CMS 20x110mm   South Africa
Yugoimport-SDPR M71/08   Serbia Single barrel development of Zastava M55
Oerlikon KAE (KAA/KAB)    Switzerland 20×128 mm Formerly known as Oerlikon 204GK/5TG
Meroka CIWS   Spain
Oerlikon KAD    Switzerland 20×139 mm Formerly known as Hispano-Suiza HS.820
GIAT M693/20 mm modèle F2   France
Rheinmetall Rh 202   Germany
Denel Land Systems GI-2   South Africa
Nexter Narwhal 20B   France Based on the 20 mm F2

Historical weapons

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Weapon Country of origin Cartridge Notes
Becker Type M2 20 mm cannon   German Empire 20×70 mm RB
Oerlikon FF   Switzerland 20×72 mm RB
Type 99 cannon, model 1   Japan
Ikaria-Werke Berlin MG FF/M cannon   Nazi Germany 20×80 mm RB
Mauser MG 151/20   Nazi Germany 20×82 mm
Ho-5 cannon   Japanese Empire 20×94 mm
Berezin B-20   Soviet Union 20×99 mm R[3]
ShVAK   Soviet Union
Helenius RK-20 APH   Finland Derivative of the Helenius RK-97 12.7 mm anti-materiel rifle
Ghan-Krnka fortress rifle   Russian Empire 20.3×95 mm R Bullet diameter 21 mm
Type 99 cannon, model 2   Japanese Empire 20×101 mm RB
Solothurn S-18/100   Switzerland 20×105 mm B
Bofors m/45   Sweden 20×110 mm
Bofors m/49   Sweden
Hispano-Suiza HS.404 and derivatives   Switzerland
Oerlikon F, FFL   Switzerland 20×110 mm RB
Polsten   Poland 20×110 mm RB
Colt Mk 12 cannon   United States 20×110 mm USN Advanced derivative of the HS.404
Madsen 20 mm anti-aircraft cannon   Denmark 20×120 mm
Type 97 automatic cannon   Japanese Empire 20×124 mm
Mauser MG 213   Nazi Germany 20×135 mm
Solothurn S-18/1000 anti-tank rifle    Switzerland 20×138 mm B
Solothurn S-18/1100 anti-tank rifle    Switzerland
ST-5 20 mm AA gun    Switzerland
FlaK 30 and FlaK 38 single-barrel AA   Nazi Germany Forerunner of Hispano-Suiza HS.820's post-war 20×139 mm round
Flakvierling quadruple-barrel AA   Nazi Germany
MG C/30L aircraft gun   Nazi Germany
Rheinmetall KwK 30 and KwK 38   Nazi Germany
Cannone-Mitragliera da 20/65 modello 35 (Breda)   Kingdom of Italy
Cannone-Mitragliera da 20/77 (Scotti)   Kingdom of Italy
Lahti L-39 anti-tank rifle   Finland Solothurn Long
Lahti L-40 anti-aircraft gun   Finland
Nkm wz.38 FK anti-tank vehicle-mounted gun   Poland Designated "heaviest machine gun", or "Najcięższy karabin maszynowy, Nkm", AA/AT (actually an autocannon)
Type 98 20 mm AA machine cannon and Type 4 20 mm twin AA machine cannon   Japan 20×142 mm
Bofors m/40   Sweden 20×145 mm R
Pansarvärnsgevär m/42   Sweden 20×180 mm R Recoilless rifle

Naming conventions

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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

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  • 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

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References

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  1. ^ PGU-27A/B TP/ PGU-28A/B SAPHEI / PGU-30A/B TP-T
  2. ^ "Otomatik Orta Kalibre Top". 17 October 2022. Retrieved 17 October 2022.
  3. ^ 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.
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