The extremely mixed outcomes of the design process led to an appropriate conclusion. On September 9, 1942, the Ural Heavy Machinery Plant’s chief engineer, M. G. Umnyagin, received a letter signed by the chief of the GABTU’s Armor Directorate, Eng. Col. S. A. Afonin, that stated the following:
In response to your letter No. 3707/48s of August 24, 1942, regarding the U-19 self-propelled gun project with a 203 mm howitzer on the KV-1 chassis, I hereby inform you of the following:
1. With the U-19 weighing 66 tonnes and with retention of the KV-1 tank transmission, the V-2K engine does not reliably support movement of the SP gun at the assigned speeds. In addition, the KV-1 tank transmission and suspension are designed for a vehicle weighing 40 tonnes and cannot perform reliably when the weight is increased to 66 tonnes.
2. The SP gun would be a highly visible target due to its height (3.51 m) and the great width of the upper part of the vehicle hull (the fixed turret).
3. The armor protection of the turret is weaker than that of a conventional KV-1; therefore, it would not provide the necessary armor protection for the crew when receiving fire from close range.
4. If the running gear is disabled, the gun can only be fired within a narrow sector (9°) because the U-19 does not have a rotating turret.
5. The large weight of the vehicle appears to make towing of disabled vehicles from the battlefield problematic.
6. The SP gun’s mobility would be low, judging by its power-to-weight ratio (9 hp per tonne) and ground pressure (98 kg/cm²).
Accordingly, I believe it would be inadvisable to continue working on the design for the U-19 self-propelled gun.{5}
Some paragraphs in the document are puzzling because projects like the 212 did not weigh less, had no better protection, and would be no less challenging to tow from the battlefield. Nevertheless, another bunker buster that the artillerymen wanted sank into oblivion without even reaching the mockup stage. The U-18 had no better luck, but for entirely different reasons.
Development work on installing the 152 mm howitzer in a superstructure on the KV-7 was delayed for a variety of reasons. The conceptual design was not finished until August 4, and it was proposed a month later—on September 3, 1942. A team of designers at the Ural Heavy Machinery Plant led by Gorlitsky tried their utmost to meet the military’s requirements while minimizing modifications to the KV-7. The reason for that is clear from the description of the U-18:
The self-propelled gun with the ML-20 152 mm gun is intended for destroying enemy bunkers and earth-and-timber emplacements.
The design objective for this self-propelled gun was to make maximum use of mass-produced assemblies from the KV tank and the ML-20 gun.
The most suitable base chassis for this system is the KV-7 tank. The Kirov Factory in Chelyabinsk has several dozen hulls with turrets for this tank that were intended for installation of one 76.2 mm and two 45 mm tank guns.
The regular tipping parts of the ML-20 gun did not fit in the existing KV-7 turret. Therefore, only the barrel and breech mechanism were taken from the ML-20 gun. The cradle and recoil mechanisms have been redesigned to have a shorter recoil length, which made it possible to fit the ML-20 system in the existing KV-7 turret.
The mounting parts were also redesigned. This solution presented advantages with respect to the turret weight and, especially, the system’s height.{6}
The U-18’s artillery system comprised only 13 assemblies, and the KV-7 hull and superstructure were not modified. It appeared that the military’s requirements were fully satisfied and the system could be put into service, especially since extra hulls were available. But a problem arose from an unexpected corner.
On September 24, 1942, the Ural Heavy Machinery Plant’s chief engineer, M. G. Umnyagin, received a letter signed by Eng. Col. Kovalev, chief of the 6th Department of the GABTU’s Armor Directorate:
In response to your letter No. 3655/48s of September 4, 1942, concerning the U-18 self-propelled gun project, I hereby inform you that a similar project proposed by Comrade Petrov between September 12 and September 14, 1942, was discussed at a meeting of the Technical Committee of the Council of the People’s Commissariat of Arms.{7}
That put an unexpected end to the history of heavy SP gun development by the Ural Heavy Machinery Plant’s design bureau. Gorlitsky worked on no more heavy self-propelled systems. How did Petrov happen to get at cross purposes with Gorlitsky?
In February 1942, artillery production was transferred from the Ural Heavy Machinery Plant to the People’s Commissariat of Arms Factory No. 8, which had been evacuated to Sverdlovsk in the fall of 1941. B. A. Fradkin stayed on as its director. In March 1942, Factory No. 8’s design bureau developed the ZIK-1 85 mm tank gun for the T-34 and KV-1 tanks. The ZIK-1 thus remained a project, but it became the first project of the design bureau headed by F. F. Petrov. Not one system with the ZIK designation (named after the Kalinin Factory) was ever put into service, but by 1943 the creations of Factory No. 9 acquired from Factory No. 8 in the fall of 1942 had begun destroying the enemy. These were the famous tank and self-propelled guns D-5 (SU-85, KV-85, and the initial T-34-85), the D-25 (IS-2, ISU-122, and IS-3), and the D-10 (SU-100), as well as the D-1 152 mm howitzer. The creations of Petrov’s OKB-9 design bureau beat out the handiwork of the famous designer V. G. Grabin in competitions. But that would come later. In 1942, the team in the chief designer’s department at Factory No. 8 was working in many different areas.
It so happened that a direct competition began in the summer of 1942 between Factory No. 8’s design bureau and Ural Heavy Machinery Plant’s design bureau for several projects, including a heavy SP gun. The situation was made particularly poignant by the fact that Gorlitsky’s design bureau was located on the fifth floor of the Ural Heavy Machinery Plant’s administration building, and Petrov’s design bureau was on its fourth floor.
Exactly when KB-3 of the chief designer’s department at Kalinin Factory No. 8 began working on the competitor to the U-18 is not known. According to documentation, task No. 5400072 for designing the “installation of the tipping parts of the 152.4 mm howitzer model 1937 (ML-20) in the KV-7 tank…” was issued by the GAU’s Artillery Committee on June 4, 1942. This date is somewhat at variance with a letter from GAU Artillery Committee chief Col. Gen. V. I. Khokhlov to Prof. E. A. Satel, chairman of the Technical Council of the People’s Commissariat of Arms. That letter was also dated June 4, 1942 and read in part:
The design department of Factory No. 8 is currently developing conceptual designs for the following self-propelled howitzers:
a) The M-30 122 mm division-level howitzer for installation in a T-34 tank;
b) The U-11 122 mm tank howitzer for installation in a T-34 tank;
c) The ML-20 152 mm gun-howitzer for installation in a KV-7 tank.