SIG MKMO

The SIG MKMO is a submachine gun produced by Schweizerische Industrie Gesellschaft (SIG) company in Neuhausen from 1933 to 1937. The MKMO – M = Maschinen, K = Karabiner M = Militär, O = Oben (Top ejection) – was designed for the military and to increase firepower it had a larger-capacity magazine as well as a longer barrel. Only 1,228 of these guns were produced. It saw limited adoption by Swiss police departments and the Swiss Guard at the Vatican. Finland purchased approximately 282 of the original MKMO variant, which were used by the home guard, supply units and coastal defense forces in the Continuation War. The SIG MKMO used a hesitation-locked operating system which kept the cartridge within the chamber long enough for the pressure within the barrel to decrease to a safe level. This system was adapted by Gotthard End based on a John Pedersen design first used in the Remington Model 51 pistol. It was also the first personal weapon to have a folding magazine well so that the magazine and mag well could be pivoted horizontally and stored within the wooden fore-stock. This made transportation during non-combat movement easy and much less difficult compared to traditional magazine wells. A simple catch system would release the magazine allowing for quick deployment. The locked-breech blowback system mirrored that of John Pedersen's Remington Model 51 only with a locking recess above rather than below the bolt. When the firearm is in battery, the breech block rests slightly forward of the locking shoulder in the frame. When the cartridge is fired, the breech block and bolt carrier move together a short distance rearward powered by the energy of the cartridge as in a standard blowback system. When the breech block contacts the locking shoulder, it stops, locking the breech. The bolt carrier continues rearward with the momentum it acquired in the initial phase. This delay allows chamber pressure to drop to safe levels while the breech is locked and the cartridge slightly extracted.