Object 701-3, the unfortunate IS-4 Prototype used for firing trials

Hello everyone! Today I want to show you the fourth IS-4 Prototype. This is the Object 701-3!
I was first planning on making this post a proper suggestion, but sadly due to this vehicle being just a firing trials hull and turret is was not going to be approved. So instead I’m posting here just to finish up the entire IS-4 Prototype family which I’ve all suggested!

The Object 701-3 before being used for firing trials

Quick note:

The name Object 701-3 is more an English version of the original name of the tank. The actual name is Объект 701 № 3.
As you can see in Russian the Prototypes are given a number, and this one is Number 0. But on the English side of the internet the 701-3 seems to be more widely used. And me having to constandly say Number 3, or No 3 might get a bit confusing. So I’m using Object 701-3 to be as clear as possible.

And incase you are wondering, there are seven total IS-4 Prototypes! From the Object 701-0 up to the Object 701-6!

With that out of the way, let’s continue!



The story of this tank began in 1944, she was the fourth IS-4 Prototype made. If you want to read more about the origins of the IS-4 Prototypes then check out my post on the first Prototype:

This tank (The Object 701-3) was build around mid 1944. The tank was made without a gun, or any other internals fitted, and was built to be used for live firing trials.

The Object 701-3 was build to the same design as the previous prototype, the Object 701-2, but it was given different side armour. Instead of the 160mm of side armour at a 30° angle, the Object 701-3 had 120mm at a 50° angle.
Both the Object 701-2 and Object 701-3 were to be used for live firing trials to see what results the different side armour layouts had.

A side photo of the Object 701-3

Before being send out to the firing trials, the tank was fitted with a suspension, tracks and ofcourse the entire hull and turret were made to the same specs as the other IS-4 prototypes.
The things not fitted to the tank are all the outside features like headlights and storage bins. On the inside we don’t know for sure, but most evidence leans towards there not being anything fitted on the inside. No engine, transmission, gun, etc.

But for this suggestion it would be required for me to suggest it with armaments. And for that I’m suggesting it with the 100mm S-34-I gun (Just like the Prototype that came before this one, the Object 701-2).
This tank that I’m suggesting was built to the exact same specs as the Object 701-2, just only with the different side armour for testing. I did find one other website that said the Object 701-3 had a 100mm gun. That might have been a mistake and they meant the Object 701-2 instead. Either way I think that the 100mm S-34-I gun makes the most sense.

Two photos of the tank after the firing trials, some big weakspots in the drivers hatch were identified, together with the bulge on the side of the turret for the gunner’s optic was shown to be a weakspot

After the firing trials the Object 701-3 was in quite a sorry state, with the transmission block falling of and frontal hull and turret penetrated

The results of the firing trials showed that the 120mm plate at an angle of 50° (What was fitted to the Object 701-3) proved to be superior against sub-caliber shells. And the 160mm plate at an angle of 30° (What was fitted to the Object 701-2) was superior to armour piercing shells.

It’s not known what happend to the Object 701-3 after the firing trials. It was most likely scrapped.



I would love to see this, or any other, IS-4 Prototype ingame. This one with the very angled side armour makes it stand out from all the other prototypes.

For that reason I think this one is best kept as an event vehicle. But let me know what you think in the poll above!

To wrap things up let’s compare this one to the ingame IS-4M:

Object 701-3 <|> IS-4Minnmm

4** <|> 4**
750hp V12 <|> 750hp V12
Suspension Type
Torsion bar <|> Torsion bar

Main armament
100mm S-34-I*** <|> 122mm D-25T***
Vertical guidance
-3° to +19° <|> -3° to +19°
Rate of fire (Rounds per minute)
2,5 - 8 <|> 2,2 - 3

Secondairy armament
mmmi7.62mm DT <|> 2 x 12.7mm DShK

Turret armour
~400mm <|> ~400mm
160mm <|> 250mm
160mm at 20° <|> 200mm at 35°
160mm at 30° <|> 170mm at 35°
30 - 30mm <|> 30 - 50mm

Hull armour
Frontal Upper Glacis
120mm at 61° <|> 140mm at 61°
Frontal Lower Glacis
160mm at 45° <|> 160mm at 45°
Upper Sides
120mm at 50°**** <|> 160mm at 30°****
Lower Sides
160mm at 0° <|> 160mm at 0°
Rear plate above the Transmission
120mm at 37° <|> 100mm at 37°
Rear Upper Glacis
120mm at 32° <|> 100mm at 32°
Rear Lower Glacis
120mm at 30°**** <|> 100mm at 40°****
Engine Deck
30mm <|> 30mm
30mm <|> 30mm

** = On the IS-4M the gunner and commander sit to the left of the gun and the loader to the right. This is swapped on the Object 701-3.
*** = Both guns have different benefits and downsides. It just depends on what you prefer, firerate or caliber.
**** = These two armour layouts both amount to almost the same effective thickness, but a plate at a higher angle has a higher chance to ricochet an incomming shot.



Armour layout of the Object 701-3, the bottom right drawing is the Object 701-3, bottom left is the Object 701-2

Basic stats:

  • Crew: 4 (Commander, Driver, Gunner, Loader)
  • Powerplant: 750hp V12
  • Suspension Type: Torsion bar
  • Turret traverse while targeting: 7,5 degrees/second
  • Maximum possible turret traverse: 15 degrees/second


  • Main armament: 100mm S-34-I gun**
    • Vertical guidance: -3° to +19°
    • Rate of fire: Around 5-8 rounds per minute
    • Ammunition storage: 41 rounds
    • Ammunition types: APHEBC and HE. Same as the Object 248 ingame
  • Secondairy armament: 7.62mm DT machine gun


  • Turret:
    • Mantlet: 400mm effective armour when hitting it above the barrel
    • Front: 160mm at various angles
    • Sides: 160mm at 20°
    • Rear: 160mm at 30°
    • Roof: 30mm

  • Hull:
    • Frontal Upper Glacis: 120mm at 61°
    • Frontal Lower Glacis: 160mm at 45°
    • Upper Sides: 120mm at 50°
    • Lower Sides: 160mm at 0°
    • Rear plate above the Transmission: 120mm at 37°
    • Rear Upper Glacis: 120mm at 32°
    • Rear Lower Glacis: 120mm at 30°
    • Engine Deck: 30mm
    • Bottom: 30mm

** = A gun was never fitted, and there is no direct quote from a source that says it would have had the 100mm gun. Me saying it would have had the 100mm gun is based on the fact that this tank was made to the same specs as the previous prototype (The Object 701-2), and that one was armed with the 100mm gun. But the 122mm S-34-II gun could be just as likely to be used for this vehicle.

Another blueprint of the armour layout of the Object 701-3

A photo of the rear of the Object 701-3, note the very angled side armour

That is all for now! Hope you enjoyed reading about this unique prototype.

Make sure to check out all the other IS-4 Prototypes I’ve suggested:



Primary source:

Secondairy sources:

Extra sources:

S-34-I gun: