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Object 263 Assault Gun

The development of a heavy PT-ACS based on the IS-7 tank began in 1950. Three draft versions of the project were developed. On the basis of one of the projects, a full-size wooden model of the Object 263 was made. However, in the future, all work on the project was discontinued due to the abandonment of serial production of the IS-7.

At the end of the 1940s in the Soviet Union the IS-7 heavy tank was created. It had excellent [for its time] armament and solid armor. However, a number of circumstances related to the emergence of new armor-piercing ammunition and features of the country's road network led to the closure of the project. The IS-7 was never adopted. At the same time, the undercarriage of the heavy IS-7 earned a number of positive comments, and some representatives of the country's military leadership were in no hurry to abandon it. And the 130-mm cannon was quite a tasty morsel.

In this regard, in 1950, the designers of the Leningrad Kirov Plant were tasked to create a heavy self-propelled artillery unit on the basis of the IS-7 tank. The project received the designation "Object 263", and V.S. was appointed the lead designer of the draft design. Starovoytov. Initially, three versions of the new self-propelled gun were created, differing from each other in some nuances of the design. In the course of work on “Object 263”, these options often “exchanged” various design nuances and as a result only one version remained in the program, with which it was decided to have a great future.

Since one of the main requirements for the new ACS was maximum unification with the IS-7 tank, its running gear was borrowed almost unchanged. The engine-transmission group remained the same: 12-cylinder V-shaped diesel M-50T with 1050 horsepower and a six-speed gearbox. The same can be said about the suspension, skating rinks and tracks.

In this case, the overall layout of the body was significantly adjusted. Armored self-propelled cabin was to be located in the rear of the hull, so the engine and transmission were transferred to the front. Fuel tanks, in turn, were now located in the middle part of the armored hull. The change in machine alignment associated with the repackage was offset by an increase in armor thickness.

First of all, the forehead of “Object 263” should be noted. In contrast to the forehead of the tank IS-7, It was not made on the “pike nose” system, but was a simple combination of straight panels. The main plus of the location of armored panels at an angle to each other is to increase the level of protection compared to the “direct” one.

For this reason, “Object 263” was proposed to be equipped with a front sheet 300 millimeters thick. The hull sides in the project had a much smaller thickness, from 70 to 90 mm. As for the armored cabin, it also had solid protection: a front sheet of 250 mm and sides of 70 mm each. With such armor, the Object 263 could withstand shelling from all existing cannons of medium tanks and a number of more serious guns.

The main armament of the self-propelled artillery installation "Object 263" was to be the gun S-70A. In fact, this was the further development of the C-70 cannon intended for the IS-7 tank. This project, created in the Central Artillery Design Bureau under the direction of VG Grabin ascended to another pre-revolutionary naval cannon B-7 caliber 130 millimeters. It is worth noting that in the course of several deep upgrades, the design of the gun was significantly changed and the C-70A had almost nothing in common with the original B-7 besides the caliber. The C-70A gun had solid dimensions, primarily caused by a 57.2 caliber barrel. In addition, the breech and recoil devices were no small. Because of this, the layout of the cabin was quite unusual. The breech of the cannon almost reached the rear wall of the cabin. For this reason, the latter had to be folded. It was assumed that before the start of the battle the crew would lower this part and be able to work without fear of damage to the cabin. In addition, the folded rear sheet slightly increased the floor space of the crew compartment, which could slightly ease the work of the crew.

The 130 mm gun had a very high recoil. Therefore, to the muzzle brake of the slit system and recoil devices, it was necessary to add a flip-down support device resembling a dozer blade. On the available photographs of the “Object 263” layout, it is clear that in the lowest position he held down the lowered forage leaf of the cabin. Along the sides of the cabin, on their inner side, were placed holders for ammunition. The separate loading shots were fixed on seven from each side. For convenience, the shells were located in one holder, the sleeves - in the other.

Loading the gun was the responsibility of two crew members: loader and his assistant. All in all, the crew of the SAU "Object 263" should have included five people: the commander, the driver, the gunner, and two loaders. For direct fire, the crew had a TP-47 sight, and for firing from closed positions it was proposed to equip a self-propelled gun with a TS-46 sight. The estimated rate of fire of the “Object 263” was not great - in a minute the crew could manage to make no more than one-and-a-half shots. The main reason for this was the specific layout of the cabin, which did not allow to achieve the indicators that the IS-7 tank had (about six shots). The low rate of fire, according to the opinion of the military and the developers, was to be offset by the high firing characteristics of the long-barreled gun.

In early 1951, the draft design of the new self-propelled gun was ready, and it was presented to the commission of the Ministry of Defense. The military authorities got acquainted with the works of the LKZ designers, after which the assembly of the full-scale SAU layout began. On the layout, it was planned to check some ideas and identify problems of layout, ergonomics, etc. Just a few weeks after the completion of the assembly of the “Object 263” layout from Moscow, an order came: to stop work on the project. Of course, the 130mm gun was a very good argument on the battlefield. However, the estimated mass of the new self-propelled artillery installation was at the level of 60 tons. It was 8000 kilograms less than the recently closed project of the IS-7, but still too much for practical use in the existing conditions.

The construction of self-propelled guns, theoretically, could be facilitated. But only at the cost of reducing the level of protection that would be far from the most reasonable solution. Due to the combination of advantages and disadvantages, the Main Armored Directorate decided that the Soviet Army did not need such equipment. The only constructed model of the “Object 263” was disassembled, and before the construction “in metal” never came.