The first research related to T-34 based tank destroyer dates back to the summer of 1940. Two chassis were sent to Kaliningrad plant N8 (Kalinin's plant). Two open-top turreted prototypes with 85mm AA gun 52-K were planned. However the development took longer than expected, and eventually the work was stopped.
In the autumn of 1941 plant N8 along with all staff who worked on the project were evacuated to
Sverdlovsk. Later, in November, a similar project was started. It was called U-20.
On January 3, 1942 the prototype was presented to the command of
Uralmash. The development was led by famous gun system engineer - F.F. Petrov.
The first U-20 prototype was basically a T-34 tank with open-top turret for the crew of 3. Front turret armour was 45mm, side - 20mm. Instead of 52-K gun, U-10 was used. It was basically the barrel of 85mm K-52 gun mounted on the gun carriage of 122mm howitzer M-30. This design decision allowed to decrease the overall size and get a relatively compact construction. However the gun stuck out in front of the full for some 850mm, which was considered as a huge drawback.
General blueprint
Longitudinal plan
Together with turret and its inner layout
Central Archive of the Russian Ministry of Defence, fund 81, inventory 12038, case N90
After the discussion held in the April of 1942 following the resolution of
GRAU it was stated that the project was a failure. In the meantime, the Americans were working on T35 SPG (future M10
Gun Motor Carriage).