20×138mmB

The 20×138mmB or Long Solothurn cartridge is a type of ammunition used mainly for anti-aircraft and anti-tank weapons during World War II. The designation means the caliber is 20 mm, the length of the cartridge case is 138 mm and B indicates it is a belted case. The loaded cartridge weighs 300 grams (10.7 oz).[1]

20×138mmB
20×138B cartridge and a tape measure in centimeters
TypeAnti-armor/anti-air
Place of origin  Switzerland
Service history
Used bySwitzerland, Germany, Italy, Finland, Poland
WarsWorld War II
Production history
Designed1930
ManufacturerSwiss Solothurn
VariantsLong Solothurn
Specifications
Case typeBottleneck, belted
Bullet diameter20 mm
Neck diameter20.9 mm (0.82 in)
Shoulder diameter25.5 mm (1.00 in)
Base diameter26.86 mm (1.057 in)
Rim diameter28.48 mm (1.121 in)
Rim thickness26.86 mm (1.057 in)
Case length138 mm (5.4 in)
Overall length202.7 mm (7.98 in)
Ballistic performance
Bullet mass/type Velocity Energy
120 grams (4.1 oz) 900 metres per second (2,950 ft/s) 47,000 J (34,655 ft⋅lbf) [1]

History
Three Finnish and Italian 20×138B cartridges next to a 37mm anti-tank shell

The 20×138mmB cartridge was developed by the Waffenfabrik Solothurn, a Swiss front company of Rheinmetall in the early 1930s from a less powerful cartridge 20×105mmB cartridge.

Weapon platforms

The 20×138mmB cartridge is used in the following weapons:

Switzerland

Germany

Italy

Finland

Poland
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References
  1. Johnson, Melvin M., Jr. (1944). Rifles and Machine Guns. William Morrow and Company. p. 385.{{cite book}}: CS1 maint: multiple names: authors list (link)
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