2. The design is satisfactory and essentially correct from a technical standpoint, but it has a number of flaws, including the following:
a) The problem of proper placement of shells in the tank has not been solved satisfactorily;
b) Even though the crew space is reasonably roomy, the design falls short in terms of supporting a maximum rate of fire with convenient placement of shells and proper loading tray design, nor does it ensure adequate ventilation of the fighting compartment.
3. We concur with some of the modifications the design makes to the tipping parts of the ML-20 system, specifically the manufacture of new trunnion and rear rings and a new elevating arc, and we also concur with shortening the cradle frame and eliminating the muzzle brake from the barrel.
4. We concur with Comrade Petrov’s proposal to replace the existing counterrod with a spindle-type counter-rod, along with changes to the recoil mechanism parts connected to the counter-rod. This would eliminate the cradle cap.
5. In developing the engineering drawings, the design bureau of Factory No. 8 must consider the following remarks by those present at the meeting.
a) The loading tray: instead of the one proposed, use the loading tray from Factory No. 592’s 122 mm assault gun.
b) Modify the way the ammunition is stored, paying particular attention to facilitating the work of the gun crew.
c) Keep the standard sight for firing from cover and use the elongated TOP for direct fire.
d) To allow natural ventilation and move shells into the turret, provide a hinged hatch in the rear of the turret and make it as large as possible.
e) Provide for mounting a machine gun in the rear wall of the turret.
f) If possible, provide a ball bearing in the bottom support of the gun traversing mechanism.
g) Increase the floor-to-ceiling height to 1600–1650 mm, instead of 1500 mm as designed.
6. After the design is reviewed by the GAU’s Artillery Committee, a joint decision to continue development work on the project, prepare engineering drawings, and manufacture a prototype should be made.
Because a number of design issues need to be finalized, including the proper location of the ammunition and fuel tanks and simplification of the manufacturing process for the turrets, hatches, etc., and because assignment of lead for manufacture of the system as a whole depends on collaboration between artillery and tank factories, the Technical Department of the People’s Commissariat of the Tank Industry of the USSR must be engaged to make the final decision.
7. Allow the design bureau of Factory No. 8 to continue working to improve the design in accordance with the remarks and to develop engineering drawings.
The chief designer of Factory No. 592, Comrade Sinilshchikov, should immediately send Factory No. 8 the drawings for the 122 mm assault gun’s loading tray.{12}
P. F. Solomonov, chief of the Artillery Committee’s 2nd Department, who by that time had been promoted to Engineer Major, was engaged in tracking the ZIK-20 project after September 20, 1942. As had happened in late 1941, he had to visit the factories in order to personally supervise implementation of the new designs. He stopped first in Chelyabinsk, where he met with Kotin (who then was also serving as chief designer at the People’s Commissariat of the Tank Industry) and designers from Experimental Plant No. 100 of the People’s Commissariat of the Tank Industry:
At this meeting and in negotiations with Comrade Kotin, the following decision was made: by order of the Artillery Committee, Factory No. 100 and the Kirov Factory are to manufacture a self-propelled chassis and mount an artillery package and fighting compartment equipment on it. To integrate the work done at the two factories, the Kirov Factory must send two designers to Factory No. 8 in Sverdlovsk. The factory needs to be given an updated operational requirement, because the issue of full utilization of the KV-7 hull has not been made sufficiently clear. Since it has been proposed to make the hull larger overall than the KV-7, the designers at Factory No. 100 (whose design bureau chief is Comrade Yermolayev) believe it would be better to equip the lightened hull of the KV-1S with the prism-shaped turret that has been designed.
Then the Ural Heavy Machinery Plant should make the hull; the Kirov Factory’s production shops should install the engine, transmission, and running gear; and Factory No. 100 should install the artillery package and manufacture and install the ammunition racks. Drawings of the hull with the turret are being developed at KB-100 from sketches made by Factory No. 8 and the Kirov Factory.
Agreement must be reached in the People’s Commissariat of the Tank Industry and an order elaborating on the existing agreement must be obtained from the People’s Commissar with an appropriate assignment of work and establishment of deadlines.
The conclusion of a contract with the factory must be delayed until the wooden mockup is approved and the overall design is refined.{13}
When Solomonov arrived in Sverdlovsk, he reviewed the drawings and issued the necessary instructions to the designers regarding modifications approved by the Technical Council of the People’s Commissariat of Arms. It was decided during the meeting held at Factory No. 8 to require the factory to finalize the drawings by October 25 and manufacture a wooden mockup of the system. A team of model makers and carpenters was detailed to construct the model by personal order of Factory No. 8 Director B. A. Fradkin. A designer named A. G. Usenko was assigned to oversee construction of the model. In order to ensure the project had enough designers and draftsmen, arrangements were made to return Factory No. 8 employees engaged in harvesting and logging operations.
Since Factory No. 8 lacked clear specifications for manufacturing a prototype of the system, Solomonov began drafting an operational requirement. This operational requirement, which was signed on September 25, 1942, was based on both the operational requirement for the bunker buster dating from April and on remarks about the ZIK-20 project:
I. Definition
1. The 152 mm self-propelled howitzer is a self-propelled gun made from the tipping parts of the 152 mm corps-level howitzer model 1937 (ML-20) mounted on a KV-tank chassis with a fixed prism-shaped installation.
II. Tactical role
2. The 152 mm self-propelled howitzer is intended for supporting mechanized and infantry units breaking through enemy defense lines and is used to destroy defensive fortifications, combat enemy artillery and tanks, and conduct artillery fire on assembly areas of counterattacking enemy groups.
3. The 152 mm self-propelled howitzer primarily executes fire by direct laying at close range while moving from point to point in short jumps. Fire is occasionally conducted from cover; firing from the move is expected to be rare.
III. Specifications
4. The self-propelled howitzer will be manufactured with minimal modifications to the service model of the KV tank (152 mm howitzer model 1937 and the KV-7 tank).
5. The vehicle’s overall dimensions—width, height, and line-of-fire height—must be as close as possible to the same dimensions on the KV-1 tank. The height of the tank and the line-of-fire height must not increase by more than 100 mm.