9mm Sten Machine Carbines with Photos and Manuals. Blowback-operated, the 32-round British Sten fires from an open bolt which remains to the rear on being cocked, and has a fixed firing pin on its face. Here's a special deal we're putting together for our European theater week! This set includes 3 British STEN parts kits. It includes 3 different models, the Mk2, Mk3, and Mk5. STENs are really fun guns and there's plenty information out there, especially on weapons guild on how to build a legal semi-auto! Awesome deal for anyone who loves WW2. The Sten Mark III was an even simpler version introduced by Lines Brothers, a firm of toy makers, and was issued out out by the time of the Normandy landings. While possibly the best Sten version of the Sten, it was not produced in large numbers. It's main feature was a fixed barrel and all-in-one body and casing.