A heated discussion about the technical documentation for the SP gun took place between July and September 1943. Some of the conditions for accepting SP guns were changed. According to the specifications, each SU-152 underwent routine firing tests—three supercharged rounds were fired. Since no instance of failure during firing was recorded from February to August 1943, it was decided on August 24 that only every tenth vehicle would be test-fired.
Among the issues discussed were modifications to the SU-152 design:
1) Group 06. Add a housing to protect the oil tank valve when removing shells from sleeves. The deadline for beginning production is October 1, 1943.
2) Group 04. On the fuel tank drawings, specify that an anticorrosion coating is to be applied to their inner surface after manufacture. The deadline is November 1, 1943.
3) Group 50. Eliminate the heads of bolts securing the fighting compartment roof from the field of view of the vision blocks with mirrors by replacing them with countersunk bolts. The deadline is September 15, 1943.{5}
The factory completed the drawings of the housing for protecting the oil tank by September 5. The problem with roof bolts in the field of view of the periscopic vision devices had been solved earlier, on August 30. Instead of replacing them with countersunk bolts, they were simply shifted to the side. The Chelyabinsk Kirov Factory rejected the requirement to give the fuel tanks an anticorrosion treatment on the grounds that no failures due to corrosion had been observed.
Things went smoothly for the Chelyabinsk Kirov Factory in September 1943. The first 36 SU-152’s were delivered by September 10 and another 73 were delivered by the 20th, easily surpassing its quota of 84 SP guns. That month, however, Factory No. 172 “distinguished itself” by producing a number of vehicles with technical defects. On September 3, 1943, Eng. Col. Sharonov, senior military representative of the GABTU’s Self-Propelled Artillery Office, sent letters to GAU and GABTU:
I hereby report that the ML-20S guns submitted by Factory No. 172 have defects that have repeatedly been pointed out by the Kirov Factory’s QC Department and the military acceptance office.
1. The bracket with a hole that is used to mount the ST-10 sight is not in the right location.
During the inspection of the six systems numbered 8239, 8244, 8247, 8266, 8287, and 8241, a check of the location of the bracket for the vision blocks specially made by the Kirov Factory revealed that the hole in the bracket matched the drawing on only one system, No. 3241, whereas the holes in the brackets on the other systems were out of position along all coordinates.
The shift in the location of the holes causes darkening of the field of view of the ST-10 sights
2. Systems lack the Luch system when they are shipped by the factory. In the third quarter of 1943, the factory failed to meet its quota by 40 systems. The shortfall of Luch devices is delaying timely submission and shipment of SU-152’s to the front.
3. The bubbles in sight levels sometimes break during assembly of the system, as well as during tactical drills.
The lack of replacement levels is also delaying delivery of the self-propelled guns.
I have received no answer to my message to the regional engineer of Factory No. 172 concerning these problems.
I hereby request your guidance concerning the issues I have raised.{6}
The SU-152 underwent additional changes in late September; these modifications were the last to occur in the production cycle. A border was placed around the submachine port in the superstructure’s rear plate. Much more significant changes were made to the superstructure roof, and these modifications are still causing disputes.
Reports about the SU-152 from the front made it known that a large quantity of powder gases accumulated inside the fighting compartment during firing, “poisoning” the crew. This became known both at GABTU and at the highest level. Stalin himself asked about a solution to the problem during a display of new armored vehicles at the Kremlin. N. S. Popov and V. I. Petrov wrote about the episode in their book “Without Secrets” (Bez tayn i sekretov).
The armored vehicles that had been brought to Moscow were housed at Cherkizovo Station in workshops of a factory that had been evacuated to the East. From here, on August 5, 1943, the men from the Kirov Factory watched the firing of the first salute celebrating the Red Army’s victory in the battle on the Kursk Salient. And on August 8, experimental tanks were sent under their own power to the Kremlin for display to government officials. They were placed not far from the Tsar Cannon, facing the Supreme Soviet building. Not long after, members of the State Defense Committee led by Stalin came out onto the square. Among them were V. A. Malyshev, People’s Commissar of the Tank Industry, and Col. Gen. Ya. N. Fedorenko, armored forces commander. Responding to Malyshev’s description of the vehicles’ combat capabilities, Stalin pointed to the 122 mm gun and said that it was quite impressive and well suited for a heavy tank.
That conversation took place next to the pacesetting IS-2 tank. Next, the Supreme Commander walked up to the ISU-152 SP gun. He obviously knew that the SP guns, which were called “beast killers” in the Battle of Kursk, had acquitted themselves well in combat. Approaching the vehicle, he suddenly climbed up onto its hull without the help of a ladder and, looking into the open commander’s hatch, asked how matters stood with ventilation of the fighting compartment. Someone had obviously told him that the crews in some of the first vehicles produced were being poisoned. Test driver K. Ye. Yegorov quietly answered him: “Exhaust gases do enter the vehicle, but improved ventilation has been developed for these guns. It passes three times as much air through, and the danger that the turret will fill with smoke or powder gases has been completely eliminated.”
Stalin was completely satisfied with the driver-mechanic’s competent answer and never asked any of the engineers about that again.
Unfortunately, there are a number of inaccuracies in this account, which has been cited many times. To begin with, neither an IS-2 nor an ISU-152 could have been in Red Square on August 8, 1943. The first ISU-152 prototype entered testing in October 1943, and testing on the IS-2 (IS-122) began after that. Stalin’s comment on the D-25 gun is nothing more than artistic license on the author’s part. The display actually included a production version of the SU-152 that had been produced in August, the KV-85 prototype (Object 239), the IS prototype with a D-5T (Object 240) 85 mm gun, an SU-85, and an SU-76M (SU-15M). The author was not only confused about the types of armored vehicles on display, he also got the date of the display wrong. Here is what People’s Commissar of the Tank Industry Malyshev wrote about the event in his journaclass="underline"