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.
Twenty millimeter caliber weapons are generally not used to target individual soldiers, but rather objects such as vehicles, buildings, or aircraft.
- 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)
Each weapon is listed with its cartridge type appended.
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 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 Automatkanon m/45 Sweden 20×110 mm Aircraft autocannon Automatkanon m/49 Sweden Aircraft autocannon 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 Automatkanon m/40 Sweden 20×145 mm R Autocannon Pansarvärnsgevär m/42 Sweden 20×180 mm R Recoilless anti-tank rifle
(incomplete list)
Dimensions Name Date Bullet diameter Case length Rim Base Shoulder Neck Cartridge length 20.3х95R Ghan 21 (.827) 95 (3.74) – – – – – 20х150R ~21 (~.827) 150 (5.9) – – – – –
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.
- 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.
- 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