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 10.7 oz.

History
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

 * Solothurn anti-tank rifles: S-18/1000 and S-18/1100
 * Solothurn ST-5 20mm AA Gun

Germany

 * FlaK 30 and FlaK 38 single-barrel, and Flakvierling quadruple-barrel anti-aircraft guns
 * KwK 30 and KwK 38 vehicle-mounted weapons
 * MG C/30L aircraft gun

Italy

 * Cannone-Mitragliera da 20/65 modello 35 (Breda)
 * Cannone-Mitragliera da 20/77 (Scotti)

Finland

 * Lahti L-39 anti-tank rifle
 * Lahti L-40 anti-aircraft gun

Poland

 * Nkm wz.38 FK anti-tank vehicle-mounted gun