•
T-28 Model 1934 (German designation:
T-28A) – main production model with the same machine gun turrets, and similar main turret, with the KT-28 76.2 mm gun, as the
T-35 heavy tank. During the production minor changes were introduced, such as the addition of a grille above the rear fan in 1935, two hatches replacing the larger one on the turret and the addition of a ball mount for the rear machine gun in 1936. •
T-28 Model 1938 (
T-28B) – version with the improved L-10 76.2 mm gun (from 16.5 to 26 calibres). Some older tanks were also backfitted with spare L-10 guns. The rod antenna replaced the horseshoe in early 1939. •
T-28E (
T-28C) – 1940 addition of appliqué armour in response to poor performance in Finland. Total front armour was increased to 50–60 mm, weight to 32 tonnes, and road speed dropped to 23 km/h. 111 tanks of all models (possibly including ones with conical turrets) were upgraded in late 1940. •
T-28-57-experimental version with ZiS-4 57mm high-velocity gun, contemporary of the T-34-57 and KV-1-57 experimental tanks. •
T-28-85— prototype with the improved F30 85 mm gun. •
T-28 Model 1940 – the final batch of about thirteen tanks with main conical turret similar to ones on the lateproduction T-35 tanks.
Experimental models Several
self-propelled guns, the IT-28 bridging tank, and an engineering vehicle with
mine rollers were tested on the T-28 tank chassis, but none were accepted for production. The T-29 was a prototype medium tank, a modernized T-28 with
Christie suspension - a later version of this vehicle was considered for the competition of prototypes, which led to the
T-34, but by then it was outdated (not to be confused with a Grotte tank project also called T-29). The T-28 also served as a testbed for the
KV tank suspension. == Operators ==