In 1935, development of an alternative to the T-29 began in the first office of Experimental Plant #185. The project, named Heavily Armored Tank #115, took into account the shortcomings of its predecessor. One of the vehicle's distinguishing features was the large depression/elevation angles of its gun and machine guns. Additionally, like the T-29, it was a convertible-drive tank. The preliminary design of the T-115 was ready in February 1938. Several more variants appeared later, including an exclusively tracked configuration. However, by that time, multi-turreted tanks had lost their relevance and no prototype was built.