The project works of the new tank BT-7 began in the early 30s. It was decided that 50% of tanks BT-7 have to be armed with a 76mm cannon. Installation of new weapons require the redesign of the tank’s hull. The front of the hull was extended, the machine gun was installed beside the driver. The new tower with 76.2 mm gun mod. 1927 was installed. The tank was built by May 1, 1934 and sent to the tests. The test have shown a lack of design of 76.2 mm gun installation. So 45 mm tank gun mod. 1932 was installed in the tank’s tower. The new version of the tank was built by November 7, 1934 and was sent for testing. However, the series BT-7 tanks was armed with the tower of previous BT-5 tanks.