On April 15, 1942, the GAU’s Artillery Committee met in plenary session to discuss the development of self-propelled artillery. In addition to members of the Artillery Committee, it was also attended by S. A. Ginsburg as the representative of the People’s Commissariat of the Tank Industry who oversaw self-propelled artillery issues. The plenary session came to the following decisions:
1. We hereby confirm that the requirements of the Artillery Committee of the Main Artillery Directorate of the Red Army concerning the need to have the following types of self-propelled gun systems in the inventory of the Red Army are correct:
1) Self-propelled guns for destroying bunkers;
2) Self-propelled guns for destroying tanks;
3) Self-propelled assault guns for supporting motorized infantry;
4) Self-propelled antiaircraft systems for escorting tank and motorized forces.
2. We consider it necessary to supplement the Red Army’s armament system with a self-propelled howitzer for combating earth-and-timber emplacements and concentrations of enemy personnel.
3. We believe it necessary to assign factories to manufacture the following self-propelled systems:
1) Self-propelled assault guns:
a) A USV or ZIS-3 76 mm division-level gun on a universal chassis incorporating assemblies from the T-70 tank.
Assign this project to Factory No. 37 (of the People’s Commissariat of the Tank Industry), to be assisted by Factory No. 9 (of the People’s Commissariat of Arms).
b) M-30 122 mm howitzer model 1938 on a T-34 chassis.
Assign this project to Factory No. 183 (of the People’s Commissariat of the Tank Industry) and Factory No. 8 of the People’s Commissariat of Arms).
2) BR-2 152 mm bunker busters based on a special chassis incorporating assemblies from the KV tank.
Assign this project to the Kirov Factory (of the People’s Commissariat of the Tank Industry), to be assisted by Factory No. 221 (of the People’s Commissariat of Arms). In view of the fact that chassis for this system are very difficult to obtain, we consider it advisable that this project be limited to system design.
For the time being, only mount the 152 mm gun-howitzer model 1937 in a KV-7 tank hull. Assign this project to the Kirov Factory (of the People’s Commissariat of the Tank Industry) and Factory No. 172 (of the People’s Commissariat of Arms).
3) Self-propelled antiaircraft systems:
a) Installation of the 37 mm automatic antiaircraft gun model 1939 on a universal chassis incorporating assemblies from the T-70.
Assign this project to Factory No. 37 (of the People’s Commissariat of the Tank Industry), to be assisted by Factory No. 4 (of the People’s Commissariat of Arms).
b) Install the 25 mm automatic antiaircraft gun model 1940 on the same universal chassis.
Assign this project to Factory No. 37, with assistance from Factory No. 172 (of the People’s Commissariat of Arms) (Comrade Loktev’s design bureau).
4. Due to the inability to rapidly obtain a special chassis incorporating assemblies from the T-34 tank for the 85 mm system with 360° traverse called a tank destroyer, discontinue further work on this project.
5. In order to accelerate the manufacture of self-propelled models according to paragraph 3 of this decree, we hereby request that Comrade Malyshev, People’s Commissar of the Tank Industry, and Comrade Ustinov, People’s Commissar of Arms, instruct the directors of the above-named factories to urgently conclude contracts with the GAU.
6. In order to increase the inventory of self-propelled artillery, we consider it sensible to modify captured vehicles for use as self-propelled guns mounting domestic arms.{4}
Thus, the idea of building an analog to SP gun 212 was shelved. It is true that the ML-20 could not, like the BR-2, “gnaw away” two-meter concrete walls, but it was in mass production. As far as cooperation on an SP gun based on the KV-7 was concerned, changes were made. In place of Factory No. 172, work on the gun was assigned to the Ural Heavy Machinery Plant. Cooperation between the Ural plant and the Chelyabinsk Kirov Factory continued. The project that had been underway in Sverdlovsk since the winter of 1942 was assigned the factory designation U-18. As with the U-13 and U-14, installation of the ML-20 in the KV-7 was overseen by L. I. Gorlitsky.
Under assignment from Kotin, Gorlitsky had been supervising a different heavy SP gun project, unrelated to the U-18, since April 1942. Another curious fact is that this project, which was assigned the factory designation U-19, had been sent to GAU and GABTU on August 12, 1942—three weeks before the U-18. And that was done despite the fact that installation of the ML-20 on the KV-7 was a high-priority task, and U-19 had not been mentioned. Moreover, a broad description of the U-19 dates back to May, and the drawings to mid-June of 1942. It is possible that this system was a response to the persistent demands of artillerymen for an “iron fist” to destroy bunkers by direct fire. This line of thinking is encouraged by the fact that the U-19 concept is highly reminiscent of Factory No. 221’s bunker buster projects and efforts by the Bauman Institute of Mechanical Engineering.
The U-19 project involved mounting a 203 mm howitzer model 1931 (B-4) on a KV-1 tank chassis. The primary mission of this SP gun was to destroy fortifications that less powerful systems could not handle. Like the KV-7, the base KV-1 tank underwent minimal modification: its turret platform was removed, its engine compartment bulkhead made removable, and its fuel tanks and air intakes changed. The tipping parts and top carriage of the B-4 203 mm howitzer were adopted without modification in order to keep costs down. The turret was replaced by a massive superstructure that completely covered the gun, which was installed in the fighting compartment. The superstructure partially covered the top of the engine compartment, potentially making it difficult to service the engine. The superstructure’s front plate was 75 mm thick, and it had 60 mm of armor on the side, 40 mm on the rear, and 30 mm on its roof. For installation of the howitzer barrel, the superstructure had a large hatch in its rear that included an access hatch for the crew. The design called for the roof to be removable. The front of the howitzer was protected by a massive mantlet 75 mm thick. Because the main mission of the U-19 was destruction of enemy fortifications, the elevation angle was limited to 10°. The gun’s traverse angle was also kept to a minimum—no more than 4.3° to each side, which matched the specification for the B-4 howitzer.
The military’s requirement that the chassis design changes be kept to a minimum while providing decent armor protection resulted in a very odd machine. The U-19 was calculated to weigh an estimated 66,190 kg, which exceeded even the SP gun 212A’s design parameters. Considering that the actual combat weight of manufactured models was usually somewhat greater than the design weight, the U-19 had the potential of becoming the heaviest Soviet SP assault gun, surpassing the armored version of the SU-14 for this dubious honor. In addition, putting the B-4 203 mm howitzer in an enclosed superstructure gave the system a height of 3510 mm, which was all of 50 mm lower than the armored version of the SU-14. The developers of the U-19 understood very well that these dimensions would make the SP gun an excellent target for the enemy. From the very beginning, therefore, the concept called for it to be escorted by conventional tanks.