152 mm gun M1935 (Br-2) () was a Soviet 152.4 mm heavy gun, produced in limited numbers by the Barrikady Plant in Stalingrad in the late 1930s. The most unusual feature of the gun was its tracked carriage, shared by a number of Soviet heavy artillery systems of the interwar period. Despite a number of drawbacks, most notably limited mobility and short service life of the barrel, the weapon was employed throughout the German-Soviet War; an upgraded variant with wheeled carriage, Br-2M, remained in service at least until the 1970s. Development and production B-10 Work on a long range 152 mm gun for Reserve of the Main Command units started in 1929, when the Bolshevik Plant in Saint Petersburg received from the Artillery Directorate requirements specifications for such a piece. The project received a factory index B-10. First barrel was manufactured in April 1932; it was sent for trials even before the carriage, which had an unusual tracked construction, was ready. Development and testing of the B-10 continued until 1935; a number of problems were revealed, including slow elevation, low rate of fire and short service life. As a result, the gun was not adopted. The two produced barrels were experimentally modified for firing pre-rifled projectiles and polygonal projectiles respectively. The experiments didn't produce practical results. An attempt to improve elevation speed by use of an electric motor failed to provide smooth elevation. The Soviet Navy briefly considered adopting a derived weapon as a coastal gun, in towed or self-propelled variant, the latter based on T-28 medium tank chassis. Only the towed variant, B-25, reached factory trials; eventually it was canceled because of shortcomings of the design and decision of the Army not to adopt the B-10. B-30 and Br-2 In the early 1930s the Artillery Directorate ordered a development of a "heavy artillery triplex", consisting of a 152 mm gun, a 203 mm howitzer and a 280 mm mortar utilizing the same carriage. The Bolshevik Plant and the Barrikady Plant in Stalingrad were entrusted with the development. The 152 mm gun projects were called B-30 (sometimes referred to as B-10-2-30) and Br-2 respectively. Both mated a barrel ballistically identical to that of the B-10, to a tracked carriage of the 203 mm howitzer M1931 (B-4). Late in 1936, the Bolshevik Plant delivered an experimental series of six pieces. A number of longer (55 calibres) barrels and a number of