OKMO (Opytniy Konstruktorsko-Mekhanicheskiy Otdel, ‘Experimental Design Mechanical Department’) was the main tank design team in the Soviet Union during the early 1930s. It produced the design of the T-26 infantry tank (a copy of a British design), of which about 12,000 would be produced. Most other designs from the bureau never saw the light of day, but it was here that Mikhail Koshkin, designer of the famous T-34 medium tank gained his early experience. The bureau was gutted in the Great Purge and broken up by the beginning of the Second World War.
OKMO was established in 1930 at the Leningrad "Bolshevik" Factory (later renamed S.M. Kirov Factory no. 185), under the direction of N. Barykov and S. Ginzburg. It oversaw design changes to the British Vickers E tank for construction as the T-26 light infantry tank, and later improvements to the T-26.
In 1930 OKMO also began design studies for heavy tanks. A team led by German engineer Eduard Grote worked on a 100-ton design with 107mm gun, four sub-turrets, and pneumatic suspension and servo-controls, called the T-41 or TG-5. A slightly more practical "land battleship" was the T-35 heavy tank, designed by N. Tseits's team and inspired by the British Vickers Independent.
In 1934, OKMO designed the T-43-2, a design for an amphibious tank with convertible drive—being able to run on tracks or wheels—as a possible replacement for the T-37 amphibious scout tank. It, and Moscow Factory no. 37's competing T-43-1 were both rejected in favour of continuing T-37 production.
Also in 1934, N. Barykov and N. Tseits worked with graduate students from the Leningrad Technical Institute to modernize the multi-turreted T-28 medium tank by adding a Christie suspension. The resulting T-29-5 adopted the convertible running gear from the BT fast tank. Further T-29-4 and T-29-1 prototypes were built in 1935, but in testing at the NIIBT in Kubinka none of these were found satisfactory. Following Soviet armoured experience in Spain, another version was built with thicker armour and a better gun—it was considered for the A-20/T-32 competition which led to the famous T-34 medium tank, but by this time was obviously outdated. (One of the Leningrad engineering students had been Mikhail Koshkin, the T-34's chief designer)
In the 1930s, OKMO also designed a number of self-propelled artillery and antiaircraft guns, and tracked infantry, ammunition and fuel transporters, but only prototypes or trial batches of any were ever built, except for the T-26-T artillery tractor.
In 1936–37 OKMO designed the T-111 (or T-46-5), the first attempt at a Soviet tank with "shell-proof" armour, effective against more than just small arms. The engine and gun were inadequate, and only a prototype was built.
The T-100 ‘Sotka’ was a two-turreted heavy tank prototype rejected in favour of the KV-1 heavy tank. OKMO tried to resurrect the T-100 as a self-propelled gun with a fixed superstructure, the SU-100Y, but this was not accepted for production either. The bureau started work on the T-50 infantry tank in 1939, but was gutted during the Great Purge. The T-50 was handed over to the K.E. Voroshilov Factory no. 174, and a few were finally produced in Omsk by February 1942, after the factory had been split up and evacuated to the Urals.