“IP” AGAINST THE “TIGER”

 

In the first half of June, the two gun — With-cacb 31 and D-5T plant No. 9 was prepared. C-31 developed by superimposing a 85-mm gun cradle 76 mm serial tank gun ZIS-5, which could greatly facilitate its production. As for the D-5T, it was a variant gun D-5C, designed for self-propelled artillery units SU-85, and was distinguished by low weight and small length of the rollback. These guns were installed in prototypes of tanks KV-85 and is-85, which is 31 July 1943 arrived in Kubinka to Netpolice for passing state tests. It was accompanied by 28 specialists, headed by the chief engineer of the plant No. 100 N. M.Sinewy. Artillery tests took place at the Gorokhovetsky artillery range. According to their results, the Board recommended that both samples to adopting Then tanks placed at the station Lesnaya in the shops of the evacuated plant No. 37. 8 August the convoy of military vehicles passed on the streets of Moscow to the Kremlin, where they were examined by Stalin, Molotov, Voroshilov, Beria, and Fedorenko, Malyshev, etc. it is Interesting to note that before the screening of the machines has removed all crew members (excluding drivers), replacing them by the NKVD.

 

September 4, 1943, the GKO decree No. 4043сс heavy tank is-85 had adopted the red Army. The same resolution experimental plant No. 100, obliged to design, manufacture and test together with tekhupravlenie, gbtu until October 15, 1943, the tank is armed with a cannon caliber 122 mm, and before November 1 ordamaged EC-152 at its base. It should be noted that the state Commission has developed a number of proposals to improve the design of the tank, part of which is under the obvious influence of foreign experience. The latter include proposals to design and test a hydraulic turret and turret anti-aircraft machine-gun mount on the commander’s turret hatch, to develop the installation in the tower of breech-loading 50-mm mortar rounds for self-defense and launch flares. It was also suggested to design a cradle that will fit 85-, 100-, 122-and 152-mm guns.

 

 

A column of tanks is-2 late releases on the way to Berlin. 3rd guards tank army, 1st Ukrainian front, spring 1945

 

First the idea of arming the ISA is an instrument of larger caliber than 85 mm. was expressed by the Director and chief designer of factory No. 100, Zh. y. Kotin. In early August 1943, studying the results of the battle of Kursk, he drew attention to the fact that of all artillery systems most successfully struggled with the “tigers” 122-mm freestanding gun mod. 1931/37 (A-19). The same conclusion was reached by the designers of the plant No. 9, which was developed and manufactured a prototype of a heavy anti-tank guns D-2 by superimposing the barrel with the ballistics of the gun A-19 on the carriage 122 mm divisional howitzer M-30. To use this powerful weapon was intended primarily to deal with heavy enemy tanks. But as soon as the barrel of such guns were mounted in the cradle and the carriage of M-30 cannon and D-2 was successfully tested, the real was the idea of the trunk A-19 heavy tank with the use of a round cradle, recoil device and the lifting mechanism from an experienced tank 122-mm howitzer U-11, as was done when creating the 85-mm guns D-5T and D-5C. This was possible only under condition of introduction in the design of the gun muzzle brake.

 

Received from factory No. 100 required documentation, in KB plant number 9 quickly perform preliminary design layout A-19 in the turret of the is-85, J. Kotin took him to Moscow: liked the project’s Commissar for tank industry V. A. Malyshev and have been approved by I. V. Stalin. GKO decree No. 4479сс from 31 Oct 1943 tank is with a 122 mm gun was adopted by the red Army. The first sample of the gun “A-19 tank” produced November 12— in the cradle D-5T mounted gun barrel D-2, removed from the carriage of M-30, with additional turning his guiding portion to the diameter of the cradle; from guns D-2 borrowed and a T-shaped muzzle brake. State tests of the tank is-122 passed very quickly and successfully. After which he was transferred to one of the suburban landfills, where of 122-mm cannon from a distance of 1500 m in the presence of Voroshilov was made a shot on an empty, already shot captured German tank “Panther”. The shell, having pierced the side armor is deployed to the right of the tower, slammed into the opposite leaf, tore it out, welding and thrown several meters. During the test the gun A-19 a ripped T-shaped muzzle brake, while Voroshilov almost died. After that the muzzle brake was replaced with another dvuhkonusnyj, German type.

 

The first serial tanks the is-85 was produced in October 1943, and is-122 in December. In parallel with Assembly of the Isov in the shops of the Chelyabinsk Kirov plant until the end of the year continued production of tanks KV-85. In January 1944 ChKZ workshops left for the last 40 IP-85, and then out of its gates in increasing numbers left, only the is-122, already equipped with the new 122-mm gun D-25T with wedge semi-automatic breech, which did little to improve the rate (of 1 — 1.5 1.5 — 2 RDS./min). From March 1944 the muzzle brake of a German type replaced by more efficient designs, cacb. Since that time the tanks of the is-85 was renamed to is-1 and is-122 — is-2.

 

However, the question of the armament of the tank is-2 after the installation of a 122 mm cannon was not closed completely. The military did not suit either low rate or small ammunition 28 rounds of separate loading ammunition — the new heavy tank. For comparison, the ammunition is-1 consisted of 59 shots, a KV-1 from 114. Besides, already after the first clashes of is-2 heavy tanks of the enemy it became clear that the standard 122 mm sharp head armor-piercing projectile BR-471 is able to penetrate the frontal armor of “Panther” only from a distance of 600 — 700 m. a weaker frontal armor “Tiger” was amazed with the distance of 1200 m, but to get this range in a German tank could only well-trained and experienced gunners. During the shelling of German tanks of powerful high-explosive grenades RP-471 the is-2 was the cracking of the welds and even the separation of the front plate by welding. The first results combat their use, confirmed, by the way, and firing tests of the tank on the ground in Kubinka in January 1944, forced designers to seek new solutions, which led to the creation of a series of prototypes of heavy tanks with guns of high power. However, in the autumn of 1944 the question of increasing panaramitee bridges of the shells dropped by itself. Gun D-25T perfectly suddenly began to hit German tanks. In the reports of the parts were descriptions of cases, when a 122-mm projectile BR-471 fired from a distance of more than 2500 m, rikoshetnoy from the frontal armor of the Panthers, leaving a huge gap. This was due to the fact that in the summer of 1944, the Germans, due to an acute lack of manganese, began to use high carbon armor, Nickel alloy and characterized by increased brittleness, especially at the welds.

 

 

 

 

The first clashes with the enemy tanks identified and under-booking the frontal part of the body Isov. In early 1944, the tank’s armor corps was trying to improve, Sakaliba it to very high hardness, but in practice this has led to a sharp increase in fragility of body parts. When firing on the range tank release in March 1944 of 76-mm gun ZIS-S with a distance of 500 — 600 m armor prolamyvayas from all sides, with the bulk of armor-piercing shells for the armor is not penetrated, but caused the formation of large masses of the secondary fragments. This fact is largely due to significant losses of tanks is-85 and is-122 in the battles of the winter — spring of 1944.

 

In February 1944 CRI-48 was given the task to conduct research on the topic “a study on the armor protection of the hull of a heavy tank is”. The work has shown that with the existing form of the frontal part of the hull it will be guaranteed from breaking through the German 75 and 88 mm shells only in the case of armor thickness not less than 145 — 150 mm (i.e., 20 — 30 mm larger than the original). On the recommendation of the TSNII-48 was changed modes of quenching, and also the design of the front part of the hull. The new building, the so-called “flattened nose”, had maintained the thickness of the armor. Of the front plate seized a hatch-stopper of the driver, significantly reducing its strength. The leaf positioned at an angle of 60° to the vertical, providing in exchange the corners of shelling ±30° no penetration of his 88-mm tank gun German Kl/To 36 even when firing at point blank range. The affected area remained lower front plate, having angle of inclination 30° to the vertical. To give it greater angle required significant modifications to the Department of management. However, given that the probability of hitting the lower front plate is less than in other parts of the body, it was decided not to touch it. With the aim of strengthening body armor lower front plate 15 July 1944 on it between the tow hooks began to place laying spare truck. “Uralmasha-water” started production of hulls with welded nose straightened in may 1944, factory No. 200 began to produce the same hull, but with a cast nose with Jun 1944. However, some time with old tanks and new buildings were issued in parallel to depletion of backlog.

 

As for the tower, to significantly strengthen her armor failed. Designed for the 85 mm gun, it was fully statically balanced. After the installation of 122 mm guns the time of balance has reached 1000 kg/m. in addition, the terms of reference involves an increase in the frontal armor up to 130mm, which would lead to even greater instability and would require the introduction of a new rotation mechanism. Since to carry out these activities without a radical change in the construction of the tower was impossible, they had to be abandoned. However, in the production process, its appearance has changed significantly. Turret of the first series of issue 1943 had a narrow recess. After setting the gun D-25T, despite the fact that her cradle was the same as that of the D-5T, the use of telescopic sight was very uncomfortable. In may 1944 started production of towers with an extended recess, which allowed to move the crosshair to the left. There was also increased armor protection of masculanity and the thickness of the lower part of the sides. Commander’s cupola displaced to the left by 63 mm, periscope sight PT-4-17 withdrew, and in its place established observation instrument MK-IV. On the commander’s turret appeared anti-aircraft heavy machine gun DShK. Until the end of the war tower ISA no other significant changes were not exposed.

 

 

Heavy tank is-2 1944— 1945

 

August 5, 1944, for special merits in developing new types of heavy tanks “Joseph Stalin” and self-propelled artillery factory No. 100 was awarded the order of Lenin. In turn for his services in organizing production of new types of tanks, self-propelled guns and tank diesel engines and equipping them red Army Chelyabinsk Kirov plant was awarded the order of the red Star. In February 1946, for outstanding achievements in the creation of new armored vehicles by J. Y. Kotin, A. S. Ermolaev. G. N. Moskvin, N. F.Shashmurin, N. Rybin, A. S. Snyde Mans, Grandparents E. P. and K. N. Ilyin became laureates of the Stalin prize.

 

In February 1944 before the red Army regiments, equipped with tanks KV were transferred to the new States. At the same time began the formation of new units, equipped with machines IP, which became known as the heavy tank regiments. While they are still in the formation was given the name of “guards.”