Solothurn S-18/100

The Solothurn S-18/100 was a 20mm anti-tank rifle used by German and Swiss forces during the Second World War, built with a semi-automatic action in a bullpup configuration. Its large, powerful ammunition gave the gun tremendous recoil and its size made it difficult to carry, and it fed from a five or ten round magazine attached horizontally to the left side of the weapon; a Finnish source credited it with armor penetration of 20mm at a sixty degree angle at 100 meters, falling to 16mm at 500 meters. A licence-free variant, the Solothurn-Arsenal, was built in small numbers, only about twenty, in Estonia before the Soviet occupation. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/