As the problem of creating a fast
tank had been solved, N.M. Toskin (as a regular military engineer)
was summoned back to the Administration of Mechanisation and
Motorisation of the Red Army to continue his service. On December
6, 1931 A.O. Firsov was appointed the Chief of the Tank Design
Further work on enhancement of the combat and technical capabilities of wheeled/tracked tank led in
1933 to replacement of the BT-2 tank by a new version of the latter - the
BT-5 tank. Very significant in this vehicle was the replacement of the imported Liberty engine by a locally produced
M-5 aviation engine designed by A.A. Mikulin. Besides, the BT-5 mounted a more powerful
45mm gun (instead of a 37mm gun installed in the BT-2). The prototype tank Model 1935
had a 76.2 mm gun. This vehicle came to be called 'artillery tank' and was intended to provide fire support for attacking
The BT-5 tanks meant for commanding personnel were manufactured equipped
with the 71-TKI radio-station with handrail aerial on the turret.
Throughout 1932-1933 design work was directed towards joining armoured parts of the hull and turret
by means of electric welding instead of rivets. The BT-2 tank with welded hull and turret
was designated the BT-4.
Carrying out further improvement of the BT series tanks,
the designers of the T2K Design Bureau created in 1935 its follow-on version
- the BT-7 tank. This tank was fitted with
a M-17T carburettor aviation engine with better characteristics, and there
were major charges to the transmission assemblies. Some of the tanks were
equipped with anti-aircraft machine guns.