Comparing: KV-5 vs. Kirovets-1

Development was started in June 1941 at the Leningrad Kirov Plant and completed by August, but the German invasion prevented development from progressing to the prototype stage. The KV-5 was expected to share some components with the KV-1. A new turret was designed, incorporating the 107-mm ZIS-6 gun. Early plans called for a new 1,200 hp diesel engine, but later adjustments, recognizing wartime disruptions, replaced this with two V-2K engines.

The Kirovets-1 project (IS-3, prototype No. 1) was developed from July through November 1944. The prototype was built at the Chelyabinsk Kirov Plant in September–October 1944. From December 18 through December 24, 1944, the vehicle underwent trials at the NIBT proving grounds in Kubinka. After it was decided to manufacture a pilot series of the modified IS-2 with a hull proposed by engineers of Plant No. 100 and Сentral Research Institute-48, the work on the Kirovets-1 was discontinued.