In addition to the sights, development was also underway on a program for using Bessemer steel to manufacture the system frame. According to People’s Commissariat of Arms Order No. 08ss of February 16, 1943, the project was assigned to Factory No. 40 of the People’s Commissariat of the Tank Industry, which had been Factory No. 592 of the People’s Commissariat of Arms until early 1943. However, that enterprise was not up to working onframes at the time: it was preparing to produce T-80 light tanks. By February 27, the factory had received the design documentation for the frame, but production of the prototypes was delayed because it lacked coke, pig iron, and foundry sand. The factory was unable to supply the first two frames for testing until March 27, and their workmanship was so poor that they were not tested. Factory No. 172 did not receive specifications for the frame until the end of May, and only one of two frames was accepted for testing. Tests were performed, during which an ML-20S system mounted on a Bessemersteel frame fired 200 rounds. The tests revealed no warping of the frame after firing, so manufacture of the component using Bessemer steel was considered a success.
Because various units and assemblies were in short supply during February 1943, 15 KV-14’s were produced instead of 30. During March, 90 systems rather than 75 were scheduled to be produced; 15 went to make up for the February shortfall. The systems were being turned out under difficult conditions: only 23 KV-14’s had been completed as of March 28. A lack of tracks was holding up production. The 90-vehicle production quota was met through truly heroic efforts during the remaining three days of the month. The Chelyabinsk Kirov Factory experienced this kind of production crisis often over the next several months.
It is also worth noting that the new SP guns only began reaching troops in the field in April—the systems had a large number of different kinds of defects, and that had an impact. In the beginning, many of the flaws were actually discovered only after the vehicles reached the troops. For example, the 1536th and 1537th SP Artillery Regiments identified defects in seven vehicles. Ten were discovered by the 1538th SP Artillery Regiment and twelve by the 1539th SP Artillery Regiment. All of this delayed the new SP gun’s debut on the front lines until July 1943. The KV-14 was not the only system haunted by such problems; virtually all Soviet SP guns had manufacturing defects that held up their delivery to troops in the field.
The first modifications to the SU-152 design (as the SP gun began to be called in late April 1943) were introduced in March 1943. Initially, the modifications were high-priority improvements that had resulted from the tests conducted on the prototype. External changes worth mentioning include the coarse aiming sight on the driver-mechanic’s vision block. It consisted of a bar welded in the middle of the observation slit. A simplified handrail design was one of the more identifiable changes. The handrails on the first SU-152’s were connected, but in March they were made separate, which simplified production. The cover over the system’s fixed mantlet was also simplified. Whereas previously it had been somewhat rounded in shape, now it was made more angular. Pickaxes were attached to the right rear side of the superstructure.
Although the SU-152 hulls were produced by just one factory, the external appearance of the SP guns varied slightly. In the beginning, the superstructure plates were cut quite precisely, but by March their appearance left something to be desired. The rear hatch, which had originally been somewhat rounded, began having a very rough shape. Little effort was going into the superstructure’s sides: they were made such that frequently the edges of the plates extended above the roof level, cutting off the view from the periscopic vision devices. The protruding edges were cut away locally so that the devices could be used. Not all SP guns had such “embellishments.” The edges of the plates could be at different heights, making each vehicle somewhat unique. In addition, until about the summer of 1943 at least two types of caps were used for the bogie brackets. In addition to the convex caps that had been used on the Chelyabinsk KV’s since 1941, some vehicles received flat caps of simplified design. They appeared on the KV-1S in early 1943. Another distinguishing feature of some SP guns was a counterweight that was sometimes attached to the mantlet. The counterweight was not a feature of a particular production run; it could be found on vehicles produced on almost any day.
Meanwhile, there were problems with component supplies in April. SU-152 assembly was held up by delays in deliveries of the artillery systems and wiring harnesses for the Luch illumination device. Due to a lack of rounds for testing the carriage, strength tests had not been performed on the gun system mount. Only the engineering had been considered during acceptance. A total of 31 vehicles were accepted by April 24 because of all of the problems with suppliers. Despite all the delays, the factory was able to fulfill the April plan for 75 vehicles, but it expected more problems the following month. Only five SU-152’s had been completed as of May 25, 1943, and the factory workers could offer no encouraging news. Factory No. 200 was the chief cause of failure this time; it had delivered only 28 hulls by May 25. There were serious problems with backlogged transmissions and other assemblies. This meant that a total of 25 SU-152’s were completed instead of 75. In addition, a number of SP guns that needed to be studied for correction of defects had accumulated at the factory. Things were no better at the beginning of June: according to reports by military representatives at the factory, it had assembled only 36 SP guns by the 10th, but not a single one of them had been completed and accepted. The reason was that a large number of engines and transmissions had been rejected because they were breaking down. The situation could not be reversed until the end of the month, and 84 vehicles were accepted instead of 75. In addition, the plan called for the factory to repair 15 SU-152’s that it had produced previously.
While SU-152’s were being produced in Chelyabinsk, events at the front were gradually causing adjustments to be made to their original role. Two German heavy Pz.Kpfw. VI Tiger Ausf. E tanks were captured on January 18, 1943, near Worker’s Settlement No. 5. One of them underwent testing in late April by being fired on with antitank and tank guns, and with divisionand corps-level artillery. The test results clearly showed that the Germans possessed a tank that could not be defeated by the majority of antitank weapons and division-level artillery. The heavy tanks that had been expected in 1941 were finally at the front. The question now became how to combat them.
