The heavy tank design bureau In Leningrad had reversed many years of Soviet practice by naming their new tank the Klimenti Voroshilov, or KV after the egregious Defence Commissar. With some courage, Koshkin told Voroshilov that the new tank should not be named after another hero of the Soviet Union; rather they should return to using the traditional designations. Koshkin suggested the designation T-34 to commemorate the 1934 state decree which ordered a massive expansion of the Soviet armoured forces. It was also the year that Koshkin had had his first ideas about the new tank. Accordingly, Koshkin's proposal was accepted.
Once the team received official sanction to build a purely tracked medium tank, they had returned to their original design for the A-32. The T-34 required thicker armour, but it also needed to be equipped with more firepower as well as a reliable transmission. Morozov and the transmission group devoted considerable time and effort to finding a solution to these problems. The two prototypes were ready by January 1940, and Koshkin took them on a gruelling trial march to prove the hardiness of the design. He drove them from Kharkov to Moscow, and here the tank was presented to the Red Army. Following this presentation, they were sent on to Finland for combat tests against the Mannerheim Line, but unfortunately they arrived too late to see any action. However, Koshkin and his team were able to demonstrate the power of the T-34's armament against captured Finnish bunkers. There were further firing trials in Minsk, and then it was on to Kiev, and finally back to Kharkov. This round trip had covered a distance of 2880km (1800 miles) in the bitter weather of February and March.
During June the drawings were completed and mass production began. The first production T-34 Model 1940 rolled out of Kharkov in September 1940. During the gruelling winter test-drive, Koshkin had contracted pneumonia, and he died on 26 September 1940. Morozov, now head of conceptual design, took over the T-34 project.
The early T-34 Model 1940 was armed with the short 76.2mm (3in) L-11 Model 1938 rifled gun with a length of 30.5 calibres. During 1941 a very small number of T-34s were fitted with the 57mm (2.24in) ZiS-4 long-barrelled high-velocity weapon, which was intended for engaging lightly armed vehicles at longer ranges. The high velocity of this weapon compensated for the loss of calibre, and the L-11 remained the standard gun on the Model 1940 production run, although it was not exactly up to the standard that the Soviets were seeking for a gun, and the T-34 designers were not totally satisfied with the weapon.
Fortunately there was a better gun available, although Soviet bureaucracy and the interference of Kulik, the head of the GAO, did much to hamper its introduction. Grabin and his team at Zavod Nr 92 already had a new 76.2mm (3in) gun in production. The F-32 was being fitted to the new KV heavy tank and was achieving much better antiarmour performance than the T-34 Model 1940s L-11, due to its longer barrel.
By the end of 1940 a member of Grabin's team, P. Muraviev, had adapted Grabin's F-32 gun for the T-34 and produced a weapon (the longer F-34 with 42 calibres) considerably superior to the L-11. In a move showing considerable initiative and courage, Grabin and the director of Zavod Nr 92, A. Elyan, began producing the F-34 alongside the L-11 and shipped them to the Kharkov plant which was building the T-34. The initial F-34 guns were completed in January 1941 and the first T-34s, usually classified as the T-34 Model 1941, armed with the F-34, rolled out in February 1941.
They were mainly used as platoon and company commander tanks, and proved very popular in combat after the German invasion, due to their increased hitting power. Stalin became aware of the new version through front-line correspondence. So as units involved in the fighting demanded more tanks equipped with the F-34, rather than the less effective L-11, the Main Defence Committee finally authorized the F-34 in the summer of 1941.The 76.2mm (3in) F-34 Model 1940 (42-calibre length) gun equipped all subsequent models ofT-34 until increases in German armour protection led to the adoption of an 85mm (3.34in) gun in late 1943, though tanks armed with the F-34 remained in service until the end of the war.