SU-85

The standard self-propelled Soviet gun, based on the T-34.
Because of the low firing rate of SU-122, the SU-85 was designed to perform a supporting role for allied tanks and infantry. It entered service in 1943 and was produced until 1944. 

The self-propelled gun was encased in a welded housing of armored plates 20 to 45 millimeters thick. It enjoyed quite a favorable reception. Its cannon could punch through a Tiger’s frontal armor from a distance of 800 meters. The gun received its baptism of fire in the Kiev offensive in November 1943. Its disadvantages includedweak armor and an unreliable suspension. Later models were much improved. 

It was eventually replaced by the more powerful SU-100.