Source: Yuri Pasholok’s blog
Author: Yuri Pasholok
Recently, Yuri Pasholok found a proposal for a very interesting IS-7 variant. What he writes in his posts is this:
IS-7 (Object 260) is one of the peaks of Soviet tank development of the late 40′s. Along with that, Object 260 was not alone. While NII-100 (SS: Soviet technology research institute No.100) was working on its project, in Chelyabinsk a new generation heavy tank was developed – the Object 705. The vehicle was supposed to have roughly the same characteristics as Object 260, but the tank design (arrangement) was different. On paper (in the project) the tank was supposed to have the 122mm BL-13 gun, but unlike Object 260, it was supposed to have the turret in the rear. This vehicle (Object 705) requires more serious research, but it’s possible to see how the vehicle would look like.
However, both the Object 705 and Object 260 were not the apex of the evolution. Apart from the Object 705 65 ton variant, Chelyabinsk design bureau worked on a 100 ton variant, designated Object 705A. It was different from the 65 ton variant in two things: armor and gun. And when it comes to the gun, we know what it would be: the 152mm experimental gun M51. Considering the Object 705 had (with 65 tons) roughly the same armor as Object 260, you can imagine what kind of monster would Object 705A be.
This is where Yuri Pasholok’s post ends. In case you are wondering, what the hell is the M51 152mm gun: an experimental Soviet gun. Barrel length was L/50. The project was ready and considered in June 1947, modifications were requested and the modified project was ready in December 1947. The gun ballistics corresponded to the 152mm BR-2 gun and the project was made so a lot of parts would be unified with 152mm M-31 gun, designed for heavy SPG’s. In order to reduce the recoil, a massive muzzle brake (that absorbed 70 percent of recoil energy) was installed. It was a very powerful weapon. However, no platform was ever created to put it on, repeating the history of 107mm ZIS-6.