The 20×138mmB cartridge was a type of ammunition used mainly for anti-aircraft and anti-tank weapons during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The designation means the caliber was 20 mm, the length of the cartridge case was 138 mm and B indicates it was a belted case. The cartridge was also known as the Long Solothurn cartridge.

History

The 20×138mmB cartridge was initially created by the Swiss Solothurn

Solothurn

The city of Solothurn is the capital of the Canton of Solothurn in Switzerland. The city also comprises the only municipality of the district of the same name.-Pre-roman settlement:...

 company in the early 1930s.

Switzerland

• Solothurn anti-tank rifles: S-18/1000
  Solothurn S-18/1000
  The Solothurn S-18/1000 20 mm Anti-Tank rifle was a Swiss and German anti-tank rifle used during the Second World War. It was a variant of the earlier S-18/100 with modifications for a higher muzzle velocity, as well as a larger cartridge size...
  
   and S-18/1100
  Solothurn S-18/1100
  The Solothurn S-18/1100 20 mm Anti-Tank Cannon was a Swiss anti-tank rifle used during the Second World War, and was a variant of the S-18/1000 with modifications for automatic fire....
  
  

Germany

• FlaK 30
  2 cm FlaK 30
  The Flak 30 and improved Flak 38 were 20 mm anti-aircraft guns used by various German forces throughout the Second World War. It was not only the primary German light anti-aircraft gun, but by far the most numerously produced German artillery piece throughout the war...
  
   and FlaK 38
  2 cm FlaK 30
  The Flak 30 and improved Flak 38 were 20 mm anti-aircraft guns used by various German forces throughout the Second World War. It was not only the primary German light anti-aircraft gun, but by far the most numerously produced German artillery piece throughout the war...
  
   anti-aircraft guns
• KwK 30
  2 cm KwK 30
  The 2 cm KwK 30 L/55 was a German 2 cm cannon used primarily as the chief weapon of the German SdKfz.121 Panzerkampfwagen II light tank...
  
   and KwK 38
  2 cm KwK 30
  The 2 cm KwK 30 L/55 was a German 2 cm cannon used primarily as the chief weapon of the German SdKfz.121 Panzerkampfwagen II light tank...
  
   vehicle-mounted weapons
• MG C/30L aircraft gun

Italy

• anti-aircraft guns: Cannone-Mitragliera da 20/65 modello 35 (Breda) and Cannone-Mitragliera da 20/77 (Scotti)
  Cannone-Mitragliera da 20/77 (Scotti)
  The Cannone-Mitragliera da 20/77 was a 20 mm anti-aircraft gun produced by the Scotti company in Italy and used by that country in World War II. It used the 20x138mmB cartridge.- History :...