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The 20 mm caliber is a common firearm bore diameter, typically used to distinguish smaller-caliber weapons, commonly called "guns", from larger-caliber "cannons" (e.g. machine gun vs. autocannon). All 20 mm cartridges have an outside projectile (bullet) diameter and barrel bore diameter of 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.


A 20×102 mm round (2nd from left) with .50 BMG rounds, golf ball, and a stick of 168-pin SDRAM computer memory
A 20×102 mm round (2nd 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 against targets such as vehicles, buildings, or aircraft.

Types of ammunition

20 mm weapons

Each weapon is listed with its cartridge type appended.

Current weapons

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 20 mm rifle  United States 20×102 mm
M61 Vulcan  United States
M197 electric cannon  United States
M39 cannon  United States
GIAT M621  France
ZVI PL-20 Plamen  Czech Republic
Metallic RT-20  Croatia 20×110 mm Hispano
Yugoimport-SDPR M71/08  Serbia Single barrel development of Zastava M55
Oerlikon 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

Historical weapons

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
ShVAK  Soviet Union 20×99 mm R
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 mmB
Solothurn S-18/1100 anti-tank rifle   Switzerland
ST-5 20mm 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 "Najciezszy karabin maszynowy, Nkm," AA/AT (actually an autocannon)
Bofors m/40  Sweden 20×145 mm R
Pansarvärnsgevär m/42  Sweden 20×180 mm R Recoilless rifle

Cartridge type 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. 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.

See also