September 8, 1943
Today, Comrades Stalin, Molotov, Voroshilov, Beria, and Shcherbakov examined the new IS, KV-85, SU-152, SU-85 and SU-76 tanks and SP guns at the Kremlin.
Comrade Stalin himself climbed up on the IS tank and the SU-152 and SU-85 (Comrade Stalin got on the tanks first). He asked detailed questions about the advantages of the new tanks, especially the IS and the SU-85.
He delivered a rebuke because the SU-152 didn’t have a fan in the fighting compartment. I promised that one would be installed within seven days.
He questioned why the IS tank with its thicker armor and more powerful gun doesn’t weigh more than the KV. I showed Comrade Stalin both tanks and pointed out to him that the IS tank is smaller than the KV and said that made it possible to reduce the weight. Comrade Stalin said: “That’s good.”
He said we need more vehicles like the SU-85. “It’s a light and agile vehicle with good mobility, and it will do a good job of beating up the German Tigers and Ferdinands,” Comrade Stalin said.
“I was impressed that at his age Comrade Stalin was able to so easily climb up on the tanks without help. He questioned the drivers and artillerymen about whether the vehicles were easy to operate, did they feel crowded, didn’t they choke on the gases, etc.”
The Chelyabinsk Kirov Factory had not worked on developing fans for the SU-152’s roof before the display. The issue was not mentioned in the list of required design improvements for the SP gun. In short, Stalin himself initiated it. On September 10, 1943, a letter over Alymov’s signature addressed to the senior military representative of the Self-Propelled Artillery Office of the Red Army’s Main Armor Directorate (USA GBTU KA), Eng. Col. Markin, arrived in Chelyabinsk:
I hereby bring to your attention that, beginning on September 23, 1943, all SU-152 self-propelled guns produced must have exhaust fans.
You are required to report when this is done.
The factory management will receive an order to this effect from the People’s Commissar of the Tank Industry.{7}
It is safe to say that this urgent task was completed on schedule. The last vehicles produced in September had fans in their roofs, and SP guns continued to be manufactured with fans until production ended.
Thanks to good management, SP gun production at the Chelyabinsk Kirov Factory proceeded like clockwork. September’s quota of 84 vehicles was met on schedule. However, this well-oiled mechanism would soon stop functioning. The IS-152 (ISU-152) SP gun went for testing in October 1943. State Defense Committee Decree No. 4504 “On the IS-152 Heavy Self-Propelled Gun with the ML-20s Gun-Howitzer,” dated November 6, accepted the new SP gun into the inventory. The IS-2 heavy tank, which served as the basis for the ISU-152, had been commissioned previously, on October 31, 1943. Thus the era of the KV heavy tanks and the SP gun based on it had come to a close.
The Chelyabinsk Kirov Factory began production engineering for the ISU-152. On the day the new SP gun was commissioned, an order discontinuing production of the SU-152 was issued. The production plan for the vehicle was cut to 42. The last SU-152’s had been manufactured by November 20, and five ISU-152’s had been delivered in Chelyabinsk by the end of the month. Some mishaps occurred because the factory was forced to produce the old vehicles while setting up to produce the new ones. A number of parts intended for the ISU-152 were made of the new grade 40 steel, and because engineering analyses of parts made of the new steel had been done incorrectly, there were numerous instances of breakage. However, the breakages were corrected based on results from company-level exercises.
The Chelyabinsk Kirov Factory delivered the last SU-152’s after production had ceased. Interestingly, these vehicles were not listed in the factory’s reports, but they are found in the reports on factory deliveries of SP guns that were sent to Stalin, Molotov, and Beria every five days. According to those reports, the Chelyabinsk Kirov Factory delivered four SU-152’s in December 1943 and the last two production vehicles in late January 1944. Including the prototype, a total of 670 SU-152’s were produced.
CHAPTER 8.
Thicker, Longer, More Powerful!
The adoption of the KV-14 did not mean that the military had finally come to a decision about the gun system needed for a bunker buster. The ML-20S was one quarter weaker than the BR-2 that the artillerymen continued to dream about. However, several things had occurred by the winter of 1943 that finally killed the BR-2 SP gun idea. People’s Commissariat of Arms Factory No. 221, the developer and producer of the BR-2 and other heavy guns, was heavily bombed in August 1942, and then it became the site of one of the bloody battles for Stalingrad. Efforts to rebuild the factory got underway in the spring of 1943, but the Soviet Union could forget about heavy guns for a long time to come.
Nevertheless, one project to mount a BR-2 on the KV-14 still took place. This project, for which only a sketch remains, was developed by a team at Factory No. 9’s design bureau under the direction of F. F. Petrov. No textual data on the project has been preserved, but the project by and large was a continuation of the idea of installing a BR-2 in the ZIK-20 SP gun that dated back to October 1942. As with the ZIK-20, they took the barrel from a BR-2 that had been modified to fit on an ML-20 cradle. A dual-chamber muzzle brake was added to the barrel to reduce recoil. Judging by a similar project to mount the BR-2 on the ZIK-20, the combat weight of the KV-14 with a heavier gun would have been 2 tonnes greater, which would have been acceptable. The later projects for the ISU-152-1 and the ISU-152-2 with the BL-8 and BL-10 guns show that Petrov’s concept of rearming the SU-152 with a BR-2 was quite feasible. However, the project did not get beyond the conceptual design stage.
As mentioned above, mounting a BR-2 on the ZIK-20 chassis was not the only concept Petrov had come up with. He also floated the idea of putting the barrel of the U-3 203 mm corps-level howitzer on an ML-20’s elevating mechanism. Matters did not proceed beyond the talking stage with the ZIK-20, but in 1943 Factory No. 9’s design bureau decided to work up a conceptual design for mounting the U-3 on the KV-14 chassis. Some scholars have taken the sketches of this project to be for the U-19 SP gun, even though there is an interval of more than six months between the two vehicles. The barrel was the only difference between the U-3 and the installation of the BR-2 on the KV-14. To reduce recoil, the barrel was given a massive, dual-chamber muzzle brake. Unlike the KV-14 with the BR-2, this brainchild of Petrov raises several questions concerning implementation. The projectile for the U-3, which was identical to that of the B-4 203 mm heavy howitzer, weighed 100 kg. It is not entirely clear how the ammunition would fit in the KV-14’s extremely narrow and low superstructure or, most importantly, how the loader would be able to load rounds into the chamber by hand. Given the low height of the KV-14’s superstructure, it would hardly be possible to fit a crane like the one on the U-19 inside it. In addition, in 1943 the heavy U-3 203 mm howitzer’s star had decidedly waned. The gun did not go into production, and that meant that the project’s future had become even more hazy. The idea of putting a U-3 barrel on an ML-20 carriage also went unrealized, although they did receive instructions to manufacture a prototype in February 1943. An upgraded version of the U-3 howitzer that received the designation U-3 BM went unrealized. It was a U-3 with a barrel lengthened to give it the ballistics of the B-4.