Question: Georgy Semyonovich Shpagin worked with Vasily Degtyaryov on a gun that fired what size cartridge?

Context paragraphs:
Degtyaryov machine gun: The Degtyaryov machine gun (Russian: Пулемёт Дегтярёвa Пехотный "Pulemyot Degtyaryova Pekhotny" "Degtyaryov's infantry machine gun") or DP-28 is a light machine gun firing the 7.62×54mmR cartridge that was used primarily by the Soviet Union starting in 1928.  The DP machine gun was supplemented in the 1950s by the more modern RPD machine gun and entirely replaced in Soviet service by the general purpose PK machine gun in the 1960s.

DShK: The DShK 1938 (ДШК, for Дегтярёва-Шпагина Крупнокалиберный, "Degtyaryova-Shpagina Krupnokaliberny", "Degtyaryov-Shpagin Large-Calibre") is a Soviet heavy machine gun firing the 12.7×108mm cartridge.  The weapon was also used as a heavy infantry machine gun, in which case it was frequently deployed with a two-wheeled mounting and a single-sheet armour-plate shield.  It took its name from the weapons designers Vasily Degtyaryov, who designed the original weapon, and Georgi Shpagin, who improved the cartridge feed mechanism.  It is sometimes nicknamed "Dashka" (familiar form of female name Daria) in Russian-speaking countries, from the abbreviation.

PPSh-41: The PPSh-41 ("pistolet-pulemyot Shpagina"; Russian: Пистолет-пулемёт Шпагина ; "Shpagin machine pistol"); is a Soviet submachine gun designed by Georgy Shpagin as a cheap, reliable, and simplified alternative to the PPD-40.  Common nicknames are ""pe-pe-sha"" (Russian: ППШ ) from its three-letter prefix and ""papasha"" (Russian: папаша ), meaning "daddy".

DS-39: DS-39 (Russian: Дегтярёва Станковый образца 1939 года ) was a Soviet medium machine gun, designed by Vasily Degtyaryov, that was used during the Second World War.  The work on the gun's design began in 1930, and it was accepted by the Red Army in September, 1939.  About 10,000 were made from 1939 to 1941, but the weapon was not successful in service and its production was discontinued after the German invasion of June, 1941, with factories converted to produce the older, more reliable Russian M1910 Maxim machine guns.  It was later replaced by the SG-43 in service.

Georgy Rodin: Georgy Semyonovich Rodin (Russian: Георгий Семёнович Родин; 19 November 1897 – 6 January 1976) was a Red Army lieutenant general.  Rodin fought in World War I as a non-commissioned officer of the Imperial Russian Army.  He joined the Red Army in 1918 and became an officer, fighting in the Russian Civil War.  In 1938, he was transferred to the reserve but returned to active duty in 1939 and led a tank battalion in the Soviet invasion of Poland.  Rodin led a tank regiment in the Winter War and became commander of a brigade in December 1940.  The brigade became the 47th Tank Division in March 1941.

7.62×45mm: The 7.62×45mm (designated as the 7,62 × 45 by the C.I.P.) is a rimless bottlenecked intermediate rifle cartridge developed in Czechoslovakia.  It is fired by the Czech vz.  52 rifle, Vz.  52 machine gun and ZB-530 light machine gun.  The round was later dropped from use when the Czech converted to the standard Warsaw Pact round, the 7.62×39mm (fired by vz.  52/57 rifle and vz.  52/57 light machine gun).  Its muzzle velocity and muzzle energy are slightly higher than that of the 7.62×39mm cartridge.

RPD machine gun: The RPD (Russian: ручной пулемёт Дегтярёва "Ruchnoy Pulemyot Degtyaryova", English: Degtyaryov hand-held machine gun) is a 7.62mm light machine gun developed in the Soviet Union by Vasily Degtyaryov for the intermediate 7.62×39mm M43 cartridge.  It was created as a replacement for the DP machine gun chambered for the 7.62×54mmR round.  It is a precursor of most squad automatic weapons.  It was succeeded in Soviet service by the RPK.

Georgy Shpagin: Georgy Semyonovich Shpagin (Russian: Георгий Семёнович Шпагин ; April 17, 1897 – February 6, 1952) was a Russian weapons designer.  He is best known as the creator of the famous PPSh-41 submachine gun, as well as working with Vasily Degtyaryov on the DShK heavy machine gun.

PPD-40: The PPD ("Pistolet-Pulemyot Degtyaryova", Russian: "Пистолет-пулемёт Дегтярёва", Degtyaryov machine pistol) is a submachine gun originally designed in 1934 by Vasily Degtyaryov.  The PPD had a conventional wooden stock, fired from an open bolt, and was capable of selective fire.  It was replaced by the PPSh-41.

Fyodorov–Shpagin Model 1922: The Fyodorov–Shpagin Model 1922 was an experimental twin barrel machine gun of Russian origin.  It was designed by Vladimir Fyodorov and Georgy Shpagin and was chambered in 6.5×51mm Fyodorov.

Supporting paragraphs: Georgy Shpagin DShK
Answer: 12.7×108mm