Sten Mk II
9x19
Created during World War II as a replacement for lost weapons lost and a much cheaper alternative to the Thompson, more than 4 million were produced. The Mark II was the most common.
It was considered inaccurate and only useful in close range and was replaced by the Sterling submachine gun in the 1950s. Some variants had a suppressor for use by the Special Operations Executive (SOE) behind enemy lines.