| 20×138mmB | |
| Origin: |  Switzerland |
| Type: | Anti-armor/anti-air |
| Used By: | Switzerland, Germany, Italy, Finland, Poland |
| Wars: | World War II |
| Design Date: | 1930 |
| Manufacturer: | Swiss Solothurn |
| Variants: | Long Solothurn |
| Is Si Specs: | yes |
| Case Type: | Bottleneck, belted |
| Bullet: | 20 mm |
| Neck: | 20.9 |
| Shoulder: | 25.5 |
| Base: | 26.86 |
| Rim Dia: | 28.48 |
| Rim Thick: | 26.86 |
| Case Length: | 138 |
| Length: | 202.7 |
| Bw1: | 4.1oz |
| Vel1: | 2950ft/s |
| En1: | 34655sigfig=2NaNsigfig=2[1] |
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 10.7oz.[1]
The 20×138mmB cartridge was developed by the, a Swiss front company of Rheinmetall in the early 1930s from a less powerful cartridge 20×105mmB cartridge.
The 20×138mmB cartridge is used in the following weapons: