In the first few months of the Great Patriotic War, many advantages and disadvantages of Soviet weapons and military equipment were manifested. Something showed excellent results, and the performance of other types in a combat situation did not live up to expectations. For example, existing tanks, including the heavy KV-1, did not always cope with the tasks assigned to them. Reservation and driving performance were sufficient, but sometimes there was not enough firepower. The troops needed a new armored vehicle with more serious weapons. In addition, the soldiers would not mind getting a tank with a comfortable fighting compartment.
In the fall of the 41st, they gathered to solve all the problems that arose at the Chelyabinsk Kirov plant. Designers L. I. Gorlitsky and N. V. Kudrin initiated the start of work on the creation of a new tank. The project was named "Object 227" or KV-7. The chassis of the KV-1 tank already mastered in the series was taken as the basis for the new armored vehicle. They decided not to change the layout of the original tank and also place the fighting compartment in the middle of the armored hull. Where big problems arose with weapons. In the fall of 1941, the 76-mm F-34 and ZiS-5 had the largest caliber among all the available tank guns. However, as it turned out from the combat use of the T-34 and KV-1 tanks in the first months of the war, they were insufficient weapons for a heavy breakthrough tank. Chelyabinsk engineers did not have the opportunity to wait for a new weapon of a larger caliber. I had to make do with the existing types of weapons.
First, there was a proposal to equip the "Object 227" with three 76-mm ZiS-5 cannons at once. According to the designers who suggested this, a battery of three guns could give the new tank sufficient firepower without requiring a significant reorganization of production and logistics. However, three 76-mm guns could not fit into the rotating turret. After a series of unsuccessful attempts to rearrange the fighting compartment or turret, the engineers decided to abandon the latter. According to the new proposal, three ZiS-5s were to be located in a fixed armored wheelhouse. Thus, the KV-7 became not a tank, but a self-propelled artillery unit. The designers from ChKZ did not set as their goal the exact observance of the terminology and continued work on the "227" theme already in the form of an ACS.
Nevertheless, even the rejection of the rotating turret gave almost no sense in equipping the new ACS with three ZiS-5 cannons. The size of the breeches and recoil devices of the guns required not only to remove the swing mechanism, but also to expand the wheelhouse to an indecent size - in this case, its side walls should have been almost beyond the level of the outer contours of the tracks. Of course, after such a preliminary design result, three ZiS-5s were rejected for uselessness. The second version of the armament of the KV-7 self-propelled gun involved the installation of one 76-mm F-34 cannon and two 45-mm 20K cannons. All three guns were proposed to be installed on one support block, designated by the U-13 index. A common cradle with three "sets" of mounts for recoil devices was mounted on a single frame. The design of the U-13 made it possible to simultaneously target all three guns in both horizontal and vertical planes. The possibility of providing each gun with its own guidance means was considered, but this possibility significantly complicated the design. It is noteworthy that during the design of the KV-7, for the first time in our country, the so-called. frame system of attachment of the tool. Subsequently, similar mechanisms will be used on almost all Soviet self-propelled guns of that time. The frame mount had great advantages over the previously used so-called. pedestal, primarily in the ergonomic aspect. The U-13 attachment point used made it possible to direct all three guns within 15 ° to the sides of the longitudinal axis in the horizontal plane and from -5 ° to + 15 ° in the vertical plane. The aiming of the F-34 and 20K cannons was carried out using the telescopic sight TMDF-7. Additional self-propelled armament consisted of three DT machine guns. Two of them were placed in ball mountings in the frontal hull sheet and the aft deckhouse sheet. In addition, the crew of six had another similar machine gun, which, if necessary, could be used as a spare or anti-aircraft gun. The self-propelled ammunition was 93 76-mm projectiles, 200 45-mm, 40 disks for machine guns and 30 grenades.
The armored wheelhouse was made of rolled armor plates with a thickness of 75 mm (forehead) to 30 mm (roof). The forehead and sides of the cabin were located at angles to the vertical plane. The cannon mask had a thickness of 100 millimeters and was made movable. In addition, the gap between the mask and the deckhouse was equipped with additional shields. The design of the armored hull of the undercarriage of the KV-1 base tank has not undergone any changes, except for modifications to install the wheelhouse. The prototype KV-7 with three guns was equipped with a 12-cylinder V-2K diesel engine with a capacity of 600 horsepower. The transmission was completely copied from the KV-1. The situation was similar with the fuel system, suspension, tracks, etc.
The assembly of the first prototype ACS project "Object 227" was completed in December 41st. Then the tests began. The driving performance of the new self-propelled gun did not differ much from the KV-1 tank - the applied chassis and the new engine affected. But on test shooting, serious problems arose. As it turned out, the KV-7 self-propelled gun simply could not simultaneously fire from all three guns, which did not allow firing more than 12 rounds per minute. Due to the different calibers and ammunition capacities, each gun, or at least each type of gun, required a separate sight. Thus, one TMDF-7 sight, intended for use with the F-34 cannon, did not cope with its duties. Another design problem emerged when firing the extreme 45mm cannons. Due to the peculiarities of the mountings of the U-13 system, a shot from the 20K cannon shifted all the guns and knocked down the aiming. Finally, a single mounting system for all three guns did not allow firing at more than one target at the same time. It was decided to continue upgrading this version of the KV-7 to improve the effectiveness of fire.
Simultaneously with the three-gun version of the "Object 227", the ChKZ design bureau also created a two-gun one. As if anticipating problems with aiming guns of various calibers, Gorlitsky and Kudrin proposed to develop a version of the self-propelled gun "227" with two guns of the same caliber. As weapons for the KV-7-II project, all the same ZiS-5 were proposed. On the basis of the mountings of the U-13 system, the U-14 was made, designed for the installation of two three-inch guns. Two ZiS-5 cannons on the U-14 were mounted on the second prototype of the new ACS. At the same time, the structure of the wheelhouse remained almost unchanged - only the mask of the guns and several other details had to be altered. I also had to redo the stowage of ammunition for the guns. The use of two identical guns made it possible to simplify its "organization" and place 150 shells in the fighting compartment. The composition and ammunition of the machine-gun armament, as well as the grenades, were transferred to the KV-7-II without any changes.
The creation of a two-cannon self-propelled gun mount took more time and tests of the KV-7-II began only in April 1942. The single caliber of both guns greatly facilitated the work of the crew, and in the future could simplify the supply problem. After several days of training, the test crew was able to achieve a combat rate of fire of 15 rounds per minute. This was more than the first version of the KV-7. However, this superiority over the three-gun vehicle was limited. The performance characteristics of the KV-7-II were exactly the same, and the ergonomics of the fighting compartment, if improved, only slightly. The situation was similar when comparing the KV-7 self-propelled guns of both versions with the original KV-1 tank.
At the end of spring 42, the question of the fate of "Object 227" reached the highest level. During the discussion of the test results and the prospects for self-propelled guns as weapons for the Red Army, a phrase sounded that put an end to its adoption. Someone from the military leadership of the Soviet Union asked: “Why do we need two or three guns? One, but good will be much better. " A number of sources ascribe these words to Comrade Stalin. However, other Soviet military leaders also did not see any advantages in the KV-7 project over the existing equipment. The installation of more powerful guns also could hardly have made the KV-7 a promising system. As a result of discussion at the top, the project was closed. The first copy of the "Object 227", equipped with three guns, was disassembled and later used as a platform for testing other equipment. A KV-7-II with two ZiS-5 cannons stood for a long time in one of the ChKZ workshops, becoming in some way a museum exhibit.
