20 x 138B cartridge

20×138mmB
Three 20×138B cartridges and a 37 mm shell.
Type	Anti-Armor/Anti-Air
Place of origin	Switzerland
Service history
Used by	Switzerland, Germany, Italy, Finland, Poland
Wars	World War II
Production history
Designed	1930
Manufacturer	Swiss Solothurn
Variants	Long Solothurn
Specifications
Case type	Bottleneck, belted
Bullet diameter	20mm
Case length	137.4 mm
Ballistic performance
Bullet mass/type Velocity Energy 4.1 ounces (120 g) 2,950 feet per second (900 m/s) 34,655 ft·lbf (46,986 J)

The 20×138mmB cartridge or Long Solothurn was a type of ammunition used mainly for anti-aircraft and anti-tank weapons during World War II. 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 loaded cartridge weighed 10.7 ounces (300 g).

The 20×138mmB cartridge was initially created by the Swiss Solothurn company in the early 1930s.

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