During the late 1920s Waffenfabrik Solothurn, a Swiss private business that emerged in the watch-making industry but later turned to the production of small-armsparts, was bought by the German concern Rheinmetall, to serve as a research and development facility away from the watchful eyes of the Allied Control Commission, established in 1918 as a result of Treaties of Versailles. In 1929 Waffenfabrik Solothurn brought out its first practical machine gun, known by the factory as the S2-100, and in export catalogs as the MG 29. Next year Solothurn announced an updated version, the S2-200, also known as theMG 30. It was, in essence, a typical light machine gun – recoil operated and magazine fed, although Solothurn also offered a complicated universal tripod for this gun. The Solothurn MG30 earned its place in history by being adopted by Austria in 1930 and Hungary in 1931 (in both cases chambered for 8x56R ammunition), and it also served as the starting point for several German machine guns, such as the MG 15 (aircraft) and MG 34. It is also must be noted that most of components of the MG30 were produced in Austria at the Steyr factory; Solothurn carried out the final assembly and test-firing.
The Solothurn S2-200 machine gun is a short-recoil operated, air cooled, magazine-fed weapon. It uses a locking ring, which is located at the end of the barrel extension, to lock the bolt. Inside the locking ring, there are six sets of locking lugs, arranged as an interrupted thread. These lugs are mated with lugs cut at the rear of the bolt. Rotation of the ring, which locks and unlocks the bolt, is controlled by rollers mounted on the outside of the ring. Upon recoil, these rollers follow cam tracks cut into the receiver. The gun is of relatively simple design, with most parts having a round cross-section. The tubular receiver is an extension of the barrel jacket. The butt hosts a tube which contains the return spring and its guide. During disassembly, the butt is unlocked and rotated to disengage it from the receiver, then removed. This permits the entire barrel / bolt group to be pulled or shaken off the receiver for replacement. Since the bolt is held attached to the barrel extension, it needs to be removed from the hot barrel and attached to the cold one before reassembly; this procedure requires a heat-insulated glove to handle the hot barrel.
The trigger is of the rocking type and allows for single shots and automatic fire. The selection of fire mode is made by pressing either the top (single shots) or bottom (automatic) part of the trigger.Ammunition feed is from curved box magazines, inserted from the left side; ejection is to the right.
The gun is normally fitted with a folding bipod, although Solothurn also produced a sophisticated universal tripod, with a remote trigger and a traverse and elevation mechanism, and recoil buffers. Modifications: S2-100 / MG 29: a direct predecessor to the S2-200, made in very limited numbers in 1929-30. Key difference from S2-200 is that buttstock cannot be removed so quickly. MG 30 (Austria): same as S2-200 except for ammunition used – it was chambered for 8x56R rimmed ammunition, which required magazines of more curved shape 31M (Hungary): same as MG 30.