Solothurn S-18/100

The gun used 20×105mm belted-case ammunition which it shared with the S 18-350 aircraft cannon that was developed from the rifle. A Finnish source gives armour penetration of the gun (probably achieved with the Hungarian APHE-T round, since it was the only type used in Finland) as 20mm at a 60-degree angle at 100-metre distance, decreasing to 16mm at 500 metres. A variant of this design, the Solothurn-Arsenal, was manufactured without license in Estonia before WW2; however only 20 were produced prior to Soviet occupation. In March 1940, with funds collected in Switzerland to help the Finnish war effort in the Winter War, Finland bought twelve S 18-154 anti-tank rifles from Solothurn, though the purchaser was nominally the Swiss army. The weapons arrived in Finland during the spring after the war had ended, but they were later used in the Continuation War. However, the guns were soon found to be obsolete in their intended role. Various models of the S-18 series, including the Solothurn S-18/1000 and the Solothurn S-18/1100 were also used by Switzerland, the Kingdom of Hungary, Nazi Germany, the Kingdom of Italy, and the Netherlands. The Waffenfabrik Solothurn firearms company was owned by the German firm Rheinmetall, and used the Swiss company to manufacture arms which were prohibited for manufacture by any German firm to get around arms limitations imposed upon them at the end of the First World War.

The Solothurn-Arsenal was a reverse-engineered copy of the S-18/100, manufactured without license in Estonia between 1938 and 1940. Apart from the prototypes, only 20 were produced and deployed with the 1st and 7th Infantry Regiment by the time of the Soviet invasion in 1940.

Bulgaria - 308 ordered in 1936 Estonia: 4 bought in 1936 for testing, reverse-engineered as Solothurn-Arsenal Finland: 12 S-18/154 Germany: some for trials Japan: 1 S-18/100 bought in 1936 for comparison with type 97 automatic cannon Hungary: Produced under license as 36M 20mm Nehézpuska and used extensively throughout WW2. Used on 38M Toldi light tank and 39M Csaba armored car. Italy: some for trials in 1934 Netherlands: 6 for trials in 1937 Switzerland: some for trials United States: 2 S-18/100 purchased in 1939 for trials at Aberdeen Proving Ground Yugoslavia