SG-43 Goryunov

The SG-43 Goryunov (Russian: Станковый пулемёт системы Горюнова, "Stankovyy pulyemyot sistyemy Goryunova", meaning "Mounted machinegun, Goryunov design") was a Soviet medium machine gun that was introduced during the Second World War. It was chambered for the 7.62×54mmR cartridge, and was introduced in 1943 as a replacement for the older M1910 Maxim machine guns. It was mounted on wheeled mounts, tripods and armored vehicles.
Design.
The SG-43 used a tilting breechblock, moving sideways and locking into the side of the receiver. The feed is not straightforward, as the gun fires the 7.62×54mmR round, and this has to be withdrawn rearwards from the belt before ramming into the breech. The reciprocating motion is achieved by using two claws to pull the round from the belt, and then an arm pushes the round into the cartridge guide ready for the bolt to carry it to the breech. Despite this complication, the SG-43 was remarkably reliable and feed jams were apparently few.
The barrel is air-cooled and massively dense, contributing to a fairly high overall weight. The bore is chromium-plated and able to withstand continuous fire for long periods. The barrel can also be easily changed by releasing a simple lock, and the carrying handle allows a hot barrel to be lifted clear without difficulty. The World War II version of the gun had a smooth outline to the barrel, and the cocking handle was under the receiver, with no dust covers to the feed and ejection ports.
History.
After the end of World War II, the SG-43 was improved and renamed SGM ("M" for modernized); dust covers and a new barrel lock were fitted, and a splined barrel was fitted to improve cooling. A coaxially-mounted stockless electric solenoid-fired variant was developed under the designation SGMT (the "T" standing for "Tankovy", or "Tank"). The SG-43M and SGMB are versions modified with dust covers and used mostly on armoured personnel carriers.
The SG-43/SGM was widely exported and also licensed for construction in several countries. It was manufactured in the People's Republic of China as the Type 53 (SG-43) and Type 57 (SGM) heavy machine guns. It was also produced in Czechoslovakia (as Vz 43) and Poland (as Wz 43).
In addition to World War II, SG-43 saw service in the Korean War with the Communist North Korean and Chinese forces. In Soviet service, the Goryunov, together with the RP-46, was replaced in the 1960s by the PK machine gun due to the switch in Soviet tactical doctrine to the general-purpose machine gun concept, rendering the gun effectively obsolete.