Comparing: KV-5 vs. IS-3A

Development began in June 1941 at the Leningrad Kirov Plant and was completed by August, but plans were interrupted due to the complicated situation on the front. The KV-5 was to utilize some components of the KV-1. A new turret was designed, incorporating the 107-mm ZIS-6 gun. Two roadwheels and a single support roller were to be added on each side. A new 1,200 h.p. diesel engine was being developed for the vehicle, however it was not completed in time and was replaced with two V-2K engines.

In 1956–1957, the Military Armored Forces Academy developed a speculative design for a new loading system on the IS-3 and T-10 heavy tanks. The IS-3 variant featured a double-row ammo rack with an automatic loading system. The crew was reduced to three members: commander, gunner, and driver. The turret was redesigned in order to accommodate the loading mechanism. The vehicle existed only in blueprints.