20 mm caliber

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.

"20mm" redirects here. For the model scale, see List of scale model sizes.

Weapons using this caliber range from anti-materiel rifles and anti-tank rifles to aircraft autocannons and anti-aircraft guns.

Usage
A 20×102mm round with .50 BMG rounds, golf ball, and a stick of 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
  • High explosive (HE)
  • High explosive incendiary (HEI)
  • Armour-piercing (AP)
  • Semi-armor-piercing high explosive incendiary (SAPHEI)
  • Armor-piercing discarding sabot (APDS)
  • High-explosive fragmentary tracer (HEF-t)
  • 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  South Africa 20×42mm
Denel NTW-20  South Africa 20×82mm Mauser
Vidhwansak  India
Anzio 20mm rifle  United States 20×102mm
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 20×110mm Hispano
Oerlikon KAA/KAB   Switzerland 20×128mm Formerly known as Oerlikon 204GK/5TG
Meroka CIWS  Spain
Oerlikon KAD   Switzerland 20×139mm 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
Ghan-Krnka fortress rifle  Russian Empire 20.3×95mm R Bullet diameter 21 mm
Type 99 cannon, model 2  Japanese Empire 20×101mm RB
Solothurn S-18/100   Switzerland 20×105mm B
Bofors m/45  Sweden 20×110mm
Bofors m/49  Sweden
Hispano-Suiza HS.404 and derivatives   Switzerland
Oerlikon F, FFL   Switzerland 20×110mm RB
Polsten  Poland 20×110mm RB
Colt Mk 12 cannon  United States 20×110mm USN Advanced derivative of the HS.404
Madsen 20 mm anti-aircraft cannon  Denmark 20×120mm
Type 97 automatic cannon  Japanese Empire 20×124mm
Mauser MG 213  Nazi Germany 20×135mm
Breda Model 35  Kingdom of Italy 20×138mm B
Nkm wz.38 FK  Poland Designated "heaviest machine gun", or "Najciezszy karabin maszynowy, Nkm," AA/AT (actually an autocannon)
Rheinmetall 2 cm KwK 30  Nazi Germany
Scotti 20 mm  Kingdom of Italy
Solothurn S-18/1000 Long   Switzerland
FlaK 38  Nazi Germany Forerunner of Hispano-Suiza HS.820's post-war 20×139mm round
Lahti L-39  Finland Solothurn Long
Bofors m/40  Sweden 20×145mm R
Becker Type M2 20 mm cannon  German Empire 20×70mm RB
Oerlikon FF   Switzerland 20×72mm RB
Type 99 cannon, model 1  Japan
Ikaria-Werke Berlin MG FF/M cannon  Nazi Germany 20×80mm RB
Mauser MG 151/20  Nazi Germany 20×82mm
Ho-5 cannon  Japanese Empire 20×94mm
Berezin B-20  Soviet Union 20×99mm
ShVAK  Soviet Union 20×99mm R

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.

See also

References
  1. PGU-27A/B TP/ PGU-28A/B SAPHEI / PGU-30A/B TP-T
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