This guns were made by Krupp. The first gun was designated as the K 12 V. The V stands for "Versuch", the tryout version. This gun had a steel cable along the barrel to provide for extra stiffness. It was operational in March 1939. The second gun, the K 12 N, was ready in July 1940. The steel cable wasn't neccesary anymore due to changes to the hydraulic system.
|Caliber||Barrel length||Gun weight||Shell weight||Rate of fire||Max range|
|21 cm||33.3 m||302 tons||107.5 kg||6 per hour||115 km|