M1931 (A-19) Russian 122mm Towed Gun

122 mm corps gun M1931/37 (A-19) (Russian: 122-мм корпусная пушка обр. 1931/1937 гг. (А-19)) was a Soviet field gun developed in late 1930s by combining the barrel of the 122 mm gun M1931 (A-19) and the carriage of the 152 mm howitzer-gun M1937 (ML-20). The gun was in production from 1939 until 1946. It saw action in World War II (primarily with corps and RVGK artillery of the Red Army) and remained in service for a long time after the end of the war. Vehicle-mounted variants of the gun were fitted to the IS-2 and IS-3 tanks of the Iosif Stalin series of tanks and the ISU-122 self-propelled gun. In 1936 the Red Army adopted the 122 mm gun M1931, also known as A-19. Unlike earlier ordnance pieces used by the Red Army, it had split trail carriage with suspension, and consequently improved mobility and traverse. The carriage of M1931 had a number of shortcomings though. The elevation mechanism was slow and unreliable; solid-tired wheels hindered mobility to some extent; there were technological problems in carriage production. Soon after the M1931, the Red Army received another artillery piece in form of the 152 mm howitzer-gun M1937 (ML-20), developed at the No. 172 Plant, under F. F. Petrov. This led to an upgrade of the M1931, handled also by Petrov's design bureau. The barrel of the M1931 was placed on the carriage of a ML-20. The improved gun successfully underwent trials in September–October 1938 and on 29 April 1939 was adopted as 122 mm corps gun M1931/37. Unusually, the new variant, like the old one, was referred to as A-19. The M1931/37 was manufactured by the Barrikady Plant in Stalingrad (1939–41), No. 172 Plant (1941–46). The number of M1931/37s manufactured can be estimated at about 2,450, not including those mounted on vehicles. Like barrel of late production M1931, the barrel of the M1931/37 was of loose liner construction, and consisted of liner, jacket and screwed-upon breech. The breechblock was of interrupted screw type, similar in construction to that of the 152 mm howitzer M1910/37. Recoil system consisted of hydraulic recoil buffer and hydro-pneumatic recuperator, both located inside the cradle under the barrel. The gun had split trail carriage adapted from the 152 mm howitzer-gun M1937 (ML-20). The carriage was fitted with leaf spring suspension and metal wheels with pneumatic tires. The carriage also featured an equilibrator. The shield gave the crew some protection from small arms and shell fragments. The M1931/37 was transported as a single piece, with barrel pulled back. It was permitted to tow the gun with barrel in its normal position, but for short distances only and with speed of no more than 4–5 km/h. Several types of artillery tractors were used: S-2 Stalinets-2, Komintern and, from 1943, Ya-12.