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Kirovets-2, also known as object 704.
The penultimate heavy assault gun. Successor to the ISU-152, and predecessor to object 268. Designed to fix several issues of the ISU-152, in game it would bridge the gap between the two. Compared to the ISU-152 it would feature much improved armour, being able to resist the 88mm KwK/PaK 43 and 128mm KwK/PaK 44. And unlike the object 268, it wouldn’t possess any major weakspot. This would however come at a slight cost to mobility, being slightly heavier than the ISU-152 with the same engine. Its gun would shoot the same shells as the regular ML-20S, but unlike the ISU-152 it featured a loading tray that slightly improved reload speed. Overall it would be closer to the object 268 than the ISU-152.
Developmental history
Spoiler
Not unlike how the IS-3 came to be, the story of Kirovets-2/object 704 also begins with the combat debut of its predecessor, the ISU-152. The ISU-152 built on the IS-1/IS-2 chassis suffered similar issues to them. In spring 1944, ChKZ was tasked with designing an improved IS-2 based on improvements of the object 701 project (IS-4), with this they were given a similar task for the ISU-152. Their IS-2 design differed from the production vehicle mainly in a reworked engine compartment and improved turret protection. A modernised gun and mantlet for the ISU-152 (ML-20SM) had been developed ever since January '44, but by the end of the year it had still not been tested in a vehicle.
ChKZ’s improved IS-2, no pictures of the prototype are known, nor believed to have survived.
It’s unclear how extensive ChKZ’s ISU-152 redesign were. It can safely be assume it received a similar if not identical engine compartment of their improved IS-2, that borrowed elements from object 701, Panther and T-34. But the ISU-152 had also been critised for its drivers position, low ammunition capacity and its frontal armour protection etc. Whether or not any of these issues were considered in the aformentioned redesign is not known. A prototype of both the improved IS-2 and improved ISU-152 were sent for trials in autumn. Though it seems both projects were abandonded in favour of what came next.
The improved IS-2 was superceeded by a new ChKZ project, the Kirovets-1. This is the vehicle that eventually became the IS-3. The Kirovets-1 impressed many at its trials, and it became clear that this was the vehicle that would replace the IS-2. As such, work on a heavy assault gun on its chassis also started shortly after, in early 1945. This project received the GABTU index 704 (Kirovets-1 received 703), and was known by ChKZ as Kirovets-2. Some call it the ISU-152 model 1945, but this name does not appear in period documents. The prototype was built in spring '45, but the ML-20SM was not installed until June. Trials of the vehicle stalled several months too, the end of the war in Europe is likely part of the reason.
Kirovets-1. IS-3 in the making. Notice it does not yet have the famous pike nose.
The new SPG inherited the 120mm thick sloped front plate of the Kirovets-1, though installed at a slightly lower angle (50° compared to 60°). It was still a considerable protection upgrade from the 90mm plate at 30° of the ISU-152. It was designed around the improved 152mm ML-20SM that had yet to be installed in an ISU-152, that gave the vehicle a coaxial mg. A first for such a vehicle. Unlike the first Kirovets-1 prototype that had received a new engine (V-11), the Kirovets-2 (and second Kirovets-1 prototype) were back to using the V-2-IS of production IS-2 tanks.
Profile of object 704.
Though it has been said by many that the Kirovets-2 was cramped and poorly designed. This is simply false. Though the vehicle was lower than the ISU-152, all of its crew positions were praised, other than that of the breech operator/second loader. Accessing ammunition for both loaders was also problematic. The ammunition capacity issue of the ISU-152 had not been addressed, the new vehicle could still only carry a total of 20 rounds for the main gun. A list of improvements were made, among them the idea to abondon the sloped sides in order to improve ammunition capacity. However by this point new requirements of a heavy SPG had already come in, and with the end of the war, the Kirovets-2 wasn’t urgently needed. The IS-3 was also only a stopgap measure until the object 701 (IS-4) was ready, and it made more sense to use its chassis.
Blueprint of assault gun on object 701 chassis, known as object 715.
Work on an IS-4 based heavy assault gun was started, with the index 715. Extremely little information about it has survived. Similarly, LKZ worked on a trio of SPG designs based on their object 260 (IS-7) tank. Their object 261 design was the closest analogue to the ISU-152. Heavily armoured, front mounted 152mm assault gun. None of these were built in metal. And work on them stopped with the decision to stop development of anything above 50 tonnes in 1949.
Model of one of LKZ’s SPG designs, object 263. This was an open topped design armed with a 130mm cannon. No known illustrations are known of the object 261 design.
It wasn’t until the T-10 came along that yet another heavy SPG would be built. This was object 268. It too was praised, but like the Kirovets-2, came too late. A true successor to the ISU-152 would never be adopted.
The T-10 based assault gun, object 268.
Specifications
Crew:
- Commander
- Gunner
- Driver
- Loader
- Loader
Weaponry:
- 152mm ML-20SM (Ammo: 20)
Elevation: -1.45°/+18° or -2°/+18°
Horizontal traverse: ?
Sights: TSh-17 - 12.7mm DShKM x2 (coaxial and AA mount) (Ammo: 300)
Dimensions:
- Weight (total): 47 300kg
- Length (total): 9050mm
Length (hull): ? - Width (total): 3070mm
- Height (total): 2240mm or 2480mm
Drivetrain:
- Engine: V-2-IS (520hp)
- Top speed: 37km/h
- Transmission:
8 forward gears
2 reverse gears
Armour: (See footnotes)
See picture
Hull:
-
Front:
Upper: 120mm at 50°
Lower: 120 or 100mm at 55° -
Sides:
Rear upper: 90 at 60° + skirts: 30mm at 15°
Middle: 90mm at 0°
Lower: 20mm at 60° -
Rear:
Upper 60mm at 46°
Lower: 60mm at 42° -
Roof: 30 or 20mm
-
Floor: 20mm
Superstructure:
- Front: 120mm at 50°
Cheeks: 90mm at 50°*
Mantlet: 260mm (160mm + 100mm) - Sides: 90mm at 45°
Lower superstructure: 90mm at 60° + skirts: 3mm at 15° - Rear
Upper: 80mm at 21°
Lower: 30mm at 21°
Footnotes:
See footnotes
- Descriptions of its armour profile are flawed in many ways, even contradictory. A better source would be preferred.
Other images:
See images
Figthing compartment of Kirovets-2. The loading tray can be seen on the left.
Kirovets-2 rear.
Sources:
-
Советские тяжелые самоходные артиллерийские установки 1941-1945. A.G. Solyankin, M.V. Pavlov, I.V. Pavlov, I.G. Zheltov. 2005.