Tuesday 20 March 2018

IS-3, Take One

"Report on experimental work at factory #100 for the first 10 days of June, 1943

Most effort at the factory was directed towards production and assembly of IS-3 components according to altered blueprints and continuation of factory trials of IS-1 and IS-2 tanks, bringing the total distance travelled to 2000 km.

Production and assembly of IS-3 components
  1. The factory #100 production plant received altered blueprints on May 25th, 1943.
  2. All components are in production aside from those that cannot be produced at factory #100: the hull, F-85 gun mount, turret, commander's cupola. The aforementioned parts are being produced at factory #200. The final drive and a portion of the drive sprocket are being produced at the Kirov factory.
  3. Most components for one vehicle have been completed and are being finished at factory #100, with the exception of the cooling fan, ammunition racks, and individual parts of other assemblies.
  4. The assembly of the drive sprocket and lower suspension has started.
  5. The gearshift gate, idler with tension mechanism, radiator, main friction clutch, speedometer control rod, planetary turning mechanism, gearbox, control rods, and brake are assembled.
  6. Casting and forging work is finished.
  7. Assembly of the hull and turret at factory #200 is being delayed due to organizational reasons and production issues. Factory #200 promises to complete assembly by June 15th, 1943.
  8. F-85 artillery systems have not yet been received.
The Kirov factory, which is scheduled to produce two IS-3 tanks, is receiving three sets of parts (one set to be used for spares)."


  1. As a former American tanker just the idea of being squeezed into the tiny JS-3 fills me with dread. I always felt that the JS-2 even with thinner armor was more practical. Though I suspect JS-3 crews were used only in breakthrough situations and didn't remain in their tanks for long, so perhaps the super thick sloped armor was the correct approach.

    1. Remember this isn't about the IS-3 made famous in the 1945 victory parade, this is the earlier "IS-3" which was the prototype of the IS tank (IS-85 later IS-1) that was then developed to the IS-2. Confused yet? :)

    2. In overall IS-3 the "pike" has wider turret, while its lower. In tests, which are translated here, you can find that both tanks had the same rate of fire.

    3. I think Jolyon Ralph's mistaken. I think this "IS-3" refers to the "IS-3, IS-4, and IS-5" designations discussed in Baryatinskiy's book which took the basic IS-2 model 1943 and tried putting different guns on them (a long-barreled, high-velocity 85 mm--the "IS-3", and the 100 D-10 ("IS-4, IS-5")).

      If I'm right this 85 mm would have had a muzzle velocity of about 1000 m/s. It was rejected as an option due to insufficient barrel strength. The IS-4 and IS-5 flipped the mantlet upside down and switched the gunner's and loader's positions; the IS-5 was deemed a success but it was decided to keep the 122 mm gun by that point.

    4. Jolyon Ralph That would explain the timeline. I kept wondering why we were talking about the article was talking about the tanks in mid 1943.I would love it if the author would clarify the matter.

    5. The soviets didn´t had an APC projectile in service to negotiate 1000m/s impact velocity until 1953.

    6. Not like they needed one anyway.

    7. There were experimental ones, but they were started as a counter to the Ferdinand. When no more Ferdinands showed up, there was little point in actually deploying it.

  2. Stewart - seems the IS-3 and IS-4 designations were used multiple times !


    In the context of this article I believe the IS-1 is the upgraded KV-13 with ZIS-5-IS 76mm gun, the IS-2 is the KV-13 with the turret almost identical to the KV-9 with the U-11 122mm howitzer, and this IS-3 (object 237) is the original IS tank prototype we recognise with six wheels per side and an 85mm gun.

    Remember, in 1943 the production IS-1 and IS-2 were known as IS-85 and IS-122 respectively, and they weren't in production in June anyway!


    ps. The IS-5 (object 248) had the S-34 100mm gun, only the IS-4 had the D-10. Only the IS-5 had the gunner and loader positions (and therefore cupola) switched, the IS-4 had a traditional layout.

  3. Jolyn--after seeing the date, I concede you're right and I was wrong. I was going to tell you this but you beat me to it.

    Baryatinskiy's book mentions the 1943 "IS-1" and "IS-2" you described but doesn't explicitly mention the "IS-3" (maybe only by Object name). So I wasn't familiar with the "IS-3" in this context, but only with the long-85 mm barreled 1944 "IS-3". Hence my error.

    I didn't have Baryatinskiy's book with me when I posted my comment, I only referred to it from memory, and you're right about the IS-4/IS-5 details too.

    1. Oops, I misspelled "Jolyon". My bad a second time!