The modernization of the T-34 was decided upon at a meeting of the State Defense Committee on August 25, 1943, after the severe losses at the battle of Kursk. V. G. Grabin, chief designer at Artillery Factory No. 92, suggesting in the spring of 1943 to us a long barrel 85 mm tank gun to up arm the T-34. He used an 85 mm gun that was going to be installed in the KV-3 heavy tank. It had to be modified to fit the T-34 and it was designated the 85 mm Tank Gun ZIS-53.
During the 1st half of 1943 another group under General F. F. Petrov work on 2 variants of the 85 mm that was later used in the KV-85, IS-1, and SU-85.
At Factory No. 92 in Gorki, A. Savin made a 3rd variant of the 85 mm gun. It was mounted in a modified T-34 turret for testing. During testing it was realized that the turret would have to be enlarged to accommodate 3 crew members to allow for the maximum possible rate of fire. The People's Commissariat for the Armor Industry assigned the task to a development bureau in the Krasnoye Sormovo factory.
However, when the 85 mm gun from V.G. Grabin was installed it was discovered that it had a limited elevation. New guns were developed and were tested at the end of 1943. The State Defense Committee approved it for introduction to the army on December 15, 1943.
|85 mm Model 1944, L/53
|85 mm Model 1944 ZIS-S-53 or 55
Other faults in the 85 mm gun from V.G. Grabin were discovered and it was decided to use the gun from General Petrov. This gun had bad ballistic performance and work continued on the ZIS-53. It was tested in January 1944 and were shortly thereafter put into production. By the end of 1944 11,778 85 mm Tank Gun ZIS S-53 were produced.
The breech block could be manually or semi-automatically operated. The recoil of the 85 mm was a hydraulic buffer and a hydro-pneumatic recuperator.
There was an elevating gear on the left that also had the triggers for the 85 mm and the machine gun. Mounted on the left wall was the traversing controls, one for manual operation and the other electrical.
The mounting of the 85 mm gun could be removed rather easily from the front of the turret with little work.
A Tsch 16 scope was installed and it had a 16 degree field of view and 4x magnification.
There were 35 rounds of the 85 mm ammunition stored in boxes on the floor, three in the rear corners, two in the front corner, four against the hull wall, and twelve in the rear bulge of the turret.
On some vehicles two MDSh smoke emitters were placed on the rear hull. They could be burned while the T-34/85 was moving or could be ejected to the ground.
Comparison of Main Tank Armament Performance
To make room for the 85 mm gun the turret ring of the original T-34/76 had to be increased. This was achieved by extending the room of the hull further back.
The turret was made from a single casting. With the sloping front of the turret, causing shot traps, it was necessary to weld deflector strips, made of metal, to the roof of the hull.
The commander was located in the rear of the turret, to the left. In front of him was the gunner. The loader was located on the right side. A cylindrical cupola for the commander was installed that had five vision slits with bullet proof glass. Early versions had hatches in the cupola that opened front and back and later versions had a single hatch. The loader had a hatch in the turret roof as well that contained two ventilators to extract gun fumes.
Pistol ports were located on the side of the turret.
The fuel tanks had to be modified, and reduced the tanks capacity in relation to the T-34/76.
Stronger springs were needed at the front to deal with the heavier turret.