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Apr 3, 2013

IS-7 - history and development

Author: Viktor Kitov (EU forum)
Published and slightly redacted by: Silentstalker

Today, we have a guest article here by Vikto Kitov about the IS-7. Enjoy!

In the spring of 1944 after  lifting the siege of Leningrad at the Kirov plant which was partially destroyed, it was decided to manufacture the ISU-152 self-propelled artillery. Tank designers were returning to the Experimental Plant № 100, after the evacuation. The leader of the team was chosen to be J. Kotin. Under his leadership, the development of a new heavy tank which was to be well armed and heavily heavy armored. Itreceived the factory designation "Object 260", and later - the index "IS-7"

-A wooden model of the IS-7-

The high level of protection of IS-7 was provided not only by an increase in the thickness of armor plates, but also due to their significant slope. The form of the front was similar to the IS-3 - "pike nose," with somewhat smoothed contours. The mass of IS-7 reached 68 tons, to ensure adequate mobility it was needed to increase the capacity of the engine. It was planned to install two diesel V-11 or B-16 with a total capacity of 1200 hp, using an electric drivetrain similar to the tried and tested on the prototype tank IS-6 ("Object 253"). However, before making the first prototype of the IS-7 the design was canceled and only a full sized wooden mock-up was build. In 1946 work on the second version started. In the same year it was decided to build two prototypes. The lead designer of the machine was engineer G. Efimov, and overall management was done by A. Ermolaev. A second version of the IS-7 would be created, rather diffrent from its predecessor.


Since work on the B-16 engine failed. The TD-30 diesel engine was installed, developed  on the ACh-300 aircraft engine. Instead of an electric transmission a traditional mechanical one was used. A serial V 12-cylinder diesel engine M-50 1050 hp at 1850 RPM was installed (used on fast offshore boats). The TH-30 aircraft engine established on the basis of ACH-300, revealed a number of significant drawbacks during the tests. The M-50 engine was distinguished by its rather large dimensions, requiring new design solutions for its installation in the tank without increasing the height of the housing. They had to develop a new short torsion suspension (so-called "beams"), consisting of seven thin rods, and such that was enough space for the engine crankcase. The case height of 2426 mm was even lower than the 300 mm on the IS-2, and 24 mm lower then the IS-3.

-Engine specifications-

Engine Type: M-50T

Manufacturer: Plant № 800
Brand: M-50T
Type: Diesel
Volume: 62,400 cm3
Maximum power: 772 kW (1050 hp) at 1850 rev / min
Maximum torque: 4606 Nm
Configuration: V12 Cylinders: 12
Bore: 180 mm Stroke: 209.8mm
Degree of compression: 13.5
Cooling: Liquid
Stroke(number of cycles): 4
Recommended fuel: DL, DZ, DA

Speed​​  60 kp/h; Cross-country speed 32 kp/h
Range- 300 km
HP per tone- 15.4
Suspension- Individual torsion
Ground pressure kgf / cm ² 0,97
Fire fighting equipment with automatic thermo sensors which activate at 100-110 ° C


The transmission for the tank was designed in two versions. The first, which was manufactured and tested in the IS-7, was a six-speed manual shift with synchronizers. Turning mechanism - a planetary, a two-step. Steering was done via a hydraulic servo.Tests showed good traction transmission quality, ensuring high average speed of the tank. The second version of the manual transmission had been developed in conjunction with the Bauman Moscow Higher Technical School.It was a planetary, 8-speed. Steering was done by hydraulic actuators with progressive gears. For the first time in the soviet tank design tracks were made with rubber-metallic hinges, hydraulic double acting shock absorbers, road wheels with internal shock absorbers operating at high loads and torsion beams.

-Electric Drive planned for the IS-6-

The first copy of the prototype was ready on September 8, the second - December 25, 1946. On field tests they showed remarkable speed for such machines- 60 km/h maximum speed and an average speed on rough road was 32 km/h. None of the heavy tanks of that time could boast with such high-speed characteristics.

Throughout 1947 in parallel with the long trials of the first two IS-7s work started on the creation of the next - better - option.

Increased armour and slope for the hull and turret after firing 88-mm, 122 mm and 128-mm shells at the prototypes on the NIIBT site at the Izhora factory. The thickness of the frontal plate was increased to 150 mm, placing them under  vertical angles of 50 ° - 52 °. The turret was given a less vulnerable form - it became more rounded, the thickness of the front was adjusted to 240 - 350 mm at an angle of 45 ° - 0 °, the side plates - to 185 - 240 mm at angles of 30 ° - 45 °. Even the most powerfull guns existing at that time (128-mm and 130-mm armor-piercing projectiles) failed to penetrate the armour.


The crew of the IS-7 consisted of five men and four of them were placed in the turret:

Commander - Right
Gunner - Left
Two Loaders - In the back, they also operated the machine guns.
The Driver was the only one to be located in the hull.


The first prototype was armed with a 130-mm S-26 gun. It used separate-case ammunition, the mass of the projectile was 33 kg. To increase the rate and ease the work of the crew a pneumatic loading mechanism was installed, developed in conjunction with the Institute of artillery.

The next version of the IS-7, was armed with a new 130-mm naval gun S-70 (7020mm long) a 54 caliber barrel and it's weight was 4225kg. The shell had a mass of 33.4 kg and an initial velocity of 900 m/s with the ability to punch through 163-mm armor, mounted at an angle of 30 °, at a distance of 1000m and 143 mm - 2,000m. Rare of fire was from 6 to 8 shots per minute thanks to the naval style "rammer" (Unconfirmed)

-S-70 Penеtration values-

Shell \ Distance--------------------------------->500---1000---1500----2000---3000 (m)
БР-482 (Angle of impact 30°)----------------->205-----195-----185----175------145 (mm)
БР-482 (Angle of impact 90°)----------------->250-----240-----225----210------180 (mm)

Keep in mind that at different times and in different countries, different methods for determining armor penetration were used. As a consequence, a direct comparison with similar data from other sources is often impossible or incorrect

-Details about the IS-7s guns-

Ammunition for the S-70 consisted of 30 shells. Rather then the bulky pneumatic loading mechanism that was used on the first machine, a smaller chain mechanism with the electric drive was developed. The characteristic difference between guns was the muzzle brake design: The C-70 used small holes, and a C-26 has a slot design.

The tank fire control unit  provided guidance, regardless of the position of the gun and fired automaticly as soon as there was a target lock. The number of machine guns on the IS-7 reached eight: Two - large caliber, and the rest - 7.62 mm RP-46. A second CPV-44 was aded on the roof of the turret for firing at air and ground targets. Aditionally two 7.62 mm machine guns and a 14.5mm were mounted in the gun mantlet. All of them had a remote control. Ammunition for the machine guns consisted of: 400 rounds of ammunition for the CPV and 2500 for the ER.

-The End-

During 1948 LKZ produced four prototypes of the new IS-7.

Following the factory tests they were handed over to the state. Chairman of the State Commission was appointed Major-General A. Owl. The main test of the Ministry of Transport Engineering of the USSR E. Kulchitsky well remembered these trials: "I was honored, I was asked first to give this remarkable machine"...With speeds exceeding 60 km/h, this heavy machine is easy to respond to the slightest force applied to the levers and pedals.The machine is totally submissive to the driver."
During a test run one of the tanks caught on fire after exeeding the period for the trials. The automatic fire extinguishing system activated twice, but the fire could not be contained. The crew had to leave the tank, and it was completely destroyed. The plastic fuel tanks, which the designers installed instead of the normal metal ones to save weight, turned out to be the source for an additional fire hazard.

Despite the outstanding performance, the IS-7 failed to receive the approval of the State Commission.

In addition to a number of failures during the test, a negative opinion of the commission affected, first and foremost, it is was too heavy. The attempt to provide the highest level of protection brought the machine to a record 68 tons - instead of the planned 65.5 tons.

The "Object 260" was not accepted for service. However, in the course of the project designers  accumulated experience, and in the later types of Soviet tanks you can see many of the tried and tested to IS-7 components.


A definite negative role in the fate of the IS-7 played another heavy tank -the 60-ton IS-4, developed and put into production at the CHKZ in 1947, after the cessation of production of IS-3. The IS-4, at the time of its creation, had the most best armor, but the  transmission wasnt reliable. It was armed with the same guns as the IS-2 and IS-3. The biggest drawback of the IS-4 was the fact that its mass was greater than the capacity of railway platforms, and highway bridges simply couldnt withstand its weight. As a result the IS-4 effectively discredited the idea of ​​a tank weighing 60 tons, which caused the skepticism of military experts regarding the IS-7.

Another explanation for the rejection of the IS-7 is that at that time the concept of increasing the role of tanks in a probable nuclear war, called for an early deployment of a large number of armored units, and thus to produce the greatest possible number of tanks in peacetime.

Blueprints and comparison

The last IS-7 (Model 1948) is in the Museum's collection of armored vehicles in Kubinka.


  1. Please,don't give it that RoF in game!It already has scout speed wtf?!I hope WG doesn't get any more ideas...

    1. i dont have problem if they give it the real life rof as long they give it the real pen cant pen anything lol

    2. If they give all tanks real life status, the british tanks will be better, and keep in mind that the ROF tested is usually in first minute of fight, if u want variable rate of fire in WoT this will do a lot of complains

  2. Scout speed? Come on.

    Have you even played it? It struggles to get to its maximum speed on flat ground with 100% crew on a highway. It is mobile,like a 50kmh E-100 x) (Not that bad).
    And its ROF won't be buffed, they plan a mobility buff.


    1. no mobility buff. top speed gets a buff, mobility/dynamic stays the same. so operational speed will still be 35ish.
      but lets wait for the test.

  3. Could the IS-7 be condersidered to be some sort of MBT? They did have excellent Firepower, which could be further improved if they fielded APDS ammo for it. Mobility, with the aftermetioned 60 km/h it is very fast and can outrun some medium tanks. And it's armour is great, at least frontally, due it's shape. It still had the weight of a heavy tank. In fact, it is the heaviest tank the soviets constructed.

    Albeit I think the IS-7 has really unreliable. Not sure if some political stuff also caused the cancellation of this project. But then again, the concept of the heavy tank was a failure in RL, at least after the war.

    Ingame, the RL performance would be OP ingame. the penetration of this gun is actually slightly higher than that in real life (not sure if they picked 30° or 90° impact angle).

    On paper the IS-7 is great..not so much in practice.

    1. No, it can hardly be classified as an MBT.

      Yes, the top speed was exelent, but it was just that- a top speed. Realistically, on a decent road I guess it could maintain 35kp/h.

      Its armour was very good against traditional AP shells. Im not sure it would fair well against more modern HEAT/HESH etc.

      I persoanly think it was canceled not because of being unreliable, but because it was hard to manufacture. And at that time the USSR was starting the mass production of the T-54.

      PS Angle is 30 if I remember correct.

    2. [i]the penetration of this gun is actually slightly higher than that in real life[/i]

      No, IRL it was 250mm @ 500m and 240mm @ 100m, so close to 260mm @ 0m, which is what WG did.

      IRL however it fired 6-8 RPM and could sustain that rof for 14 rounds (two minutes), in game that is not quite true...

      Also 130mm S-70 WAS NOT naval gun, it had unique ballistics at the time, it's ammo was developed from naval ammo, but it's unique ballistics were obtained by necking down 152mm Canet case (making practically wildcat 130-152mm), using 130mm naval gun barrel with new breachblock, which was developed for 152mm high performance field gun.

    3. > No, IRL it was 250mm @ 500m and 240mm @ 100m, so close to 260mm @ 0m, which is what WG did.


    4. It's actually S-69, S-70 could have some improvements over it.

  4. I would also like to thank Frank for posting this in such a quick manner.

  5. Poor IS-7, it's the shadow of itself in WoT, damned WG and their anti-russian bias...

  6. Replies
    1. Naah, they buff German designs that were historically bad or stupid and usually nerf Soviet designs because they would be too good.

    2. That's somewhat true, certainly the Maus didn't reach speeds of 20 kmh IRL...

    3. @Anon
      >soviet designs

    4. >Hope that was sarcasm...
      No sarcasm intended, they give 100mm to the Chinese medium VII but they refuse to give it to the Russian one because of "balance issue", IS-7 is crap compared to the historical one and they won't ever give us a Russian tier VIII medium premium, WG has an obvious anti-russian bias, only fanboys of those nazi crappy tanks wouldn't notice.

    5. Yeah "obvious", for sure. :D

      Have you cleaned your stalin portrait on the wall today? :D

    6. I did it for sure, I wonder what they're doing in Minsk though. Jokes apart, they said that IS-7 should be tier XII in order to be close to its historical counterpart, then why did they bother to put it in the game to begin with?

    7. In one of the Q&A the devs said it was one of their biggest mistakes, but by the time they realised that, it was too late to take it out of the game.

    8. Well was the IS-7 'that' good? I mean a lot of tanks look good on paper but in reality turn out less than satisfactory.

  7. Some discussion about 130mm autoloader:

    1. Interesting to note that it was indeed an *autoloader.* Look at the way the shells are facing in the picture; forwards, towards the gun breech, not backwards away from the gun breech as they would be in a manually loaded gun with power-assist rammer.

      Those two loaders are just there to keep feeding the autoloader!

  8. Everything in Russia is metric so are we talking metric tonnes (100kg) or the Imperial ton or short ton?. I assume metric tonnes in which case I would appreciate you making this clear as a tank-technophile I love the detail. Good article. I'm grinding for one in game right now.

    1. Metric system is the best.
      Less than 5 countries still use Imperial system (not Star Wars). Including USA which pisses me off.

      Ontopic: One would ask - where is the IS-5? We got all numbers up to IS-8/T-10. All could I find is that IS-5 was some sort of upgrade on IS-2.

    2. About the IS-5, it looks like an IS-1/2 with a 100mm gun, Russian wikipedia has an article about it:

    3. I can only assume it was metric tonnes.

      PS 1t= 1000kg

      About the IS-5, it doesnt seem too interesting to me. Also a lot of the good tank projects were simply named Obj 2**

    4. There were two IS-5, one was based on IS-1 but with 100mm gun (in game stock IS with 100mm D-10T is close to it), other was (IIRC Viktor could corect me)development prototype that lead to Objekt.701, ie. IS-4 development.
      Problem with tracking Soviet development is that designations and also numbers periodically repeat, we have Obj.907 medium and light tanks at same time, there were two T-34s, one well known other light tank from '30s etc etc...

    5. typo obviously 1000kg. apologies

  9. I got a question for all of you readers.
    Lets say the IS-7 never was implented as the first russian tier 10. Lets say it was the IS-4 who became the 1st top tier russian tank.
    Now we jump to the present and lets say that SerB got a new heavy line for us ending with the IS-7 at top. Would you consider it OP if it was added to the game now or would you think it was UP cus of the bad accuracy and so on.

    1. As you know the IS-7 was slightly OP/outclassing its top tier enemies like the T30 and the Maus.

  10. Frankly speaking russian tank r the best at that time n its the most op tank but HONESTLY WG DON LIKE RUSSIAN THT WHY THEY MAKE RUSSIAN TANK JUST LIKE SHI....T so no wan will play those tank n thts why russian the only nation will never ever have autoloader

  11. Simple WG DON LIKE RUSSIAN THEY ONLY LIKE American,nazi,france all frm europe the more they buff the more i will use/support only russian more sweet dream WG pls wake up face the reality RUSSIAN R THE BEST yippyyyy


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