ISU High Power Gun Projects

Author: Will Kerrs

Site: Tanks-Encyclopedia

Dedicated Beast Slayers

In mid-1944, the Red Army recognized that it might need tanks that could consistently and reliably destroy the Wehrmacht’s most well-armored tanks. The Red Army fielded few tanks that could destroy the King Tiger, Elefant, and Jagdtiger reliably from medium-long ranges. Although it is true that the ISU-122, ISU-122s, ISU-152, and IS-2 were capable of destroying German heavy tanks, their combat results were not consistent enough. As a result, starting in June of 1944, five “BM” (“High Power” – Russian: “высокой мощности”) guns were developed for the ISU chassis. The resulting vehicles were: Object 243 (ISU-122-1 with the 122mm BL-9 gun), Object 246 (ISU-152-1 with the 152mm BL-8 gun), Object 247 (ISU-152-2 with the 152mm BL-10 gun), Object 250 (ISU-130 with the 130mm S-26 gun), and Object 251 (ISU-122-3 with the 122mm S-26-1 gun). More gun projects were being developed at this time, but no others appeared to be mounted onto a chassis. The guns proved capable, on paper, of destroying tanks such as the Jagdtiger, but testing showed that they were simply not practical. Moreover, these projects took well over a year to refine, and seeing as though the war ended before they were complete, they were all dropped.

A table with comparative statistics is provided at the bottom of the article.

Context: Soviet guns against German armor

Mythbusting: The SU-152 and ISU-152 were “Beast Killers”

Soviet wartime propaganda suggested that the SU-152 and ISU-152 (SU being based on the KV chassis, ISU being based on the IS chassis) were “Beast-Killers” because they could destroy Panthers, Tigers, and Elefants. The ISU-152’s 152mm ML-20S howitzer was, indeed, capable of destroying heavy German armor, but this required a direct hit with an High Explosive (HE) shell. Such a direct hit could do one of three things to disable the tank: destroy the vehicle’s drive systems, kill its crew, or blow the turret / casemate / hull open (or even clean off, in the case of turrets). Armor Piercing (AP) and Concrete Piercing shells were developed, but these were expensive and complicated to make, hardly more effective than HE rounds, and thus were scarcely supplied – even at Kursk! However, the ISU-152 was not a dedicated tank destroyer – it was an assault gun designed for bunker busting and indirect fire. Needless to say, using an assault gun as a tank destroyer was risky business.

Firstly, the gun would need to be fired at short ranges against enemy tanks. This is because the ML-20S was a fairly low velocity howitzer, which would simply not be accurate enough to engage tanks from distances. Consider also that the vehicle had a maximum of 90 mm of armor, which meant that it whilst it was adequately protected from some German guns at long ranges, it simply was not thick enough to protect the vehicle in the short ranges it would need to operate in as a tank destroyer. For example, the 7.5 cm KwK 40 L/48, as mounted on StuGs, Panzer IVs, and Jagdpanzers, could penetrate 97 mm of armor at 500 m, and 87 mm of armor at 1000 m, at 30 degrees (the ISU-152 casemate was barely sloped at all). Also consider that the vehicle was simply not mobile enough to be engaging more nimble German tanks, and could probably be outmaneuvered anyway.

Yet another major issue of using the ISU-152 as a tank destroyer was that it could only manage 1-3 rounds per minute (depending if it had one or two loaders, and how experienced they were). This meant that in any type of ‘duel’, the ISU-152 would not only need to fire first, but also guarantee a hit, or practically any opposing German tank could get numerous shots off against it – as mentioned early, likely knock-out blows. Having said this, it did not seem to be a consideration taken into account when making the “BM” projects, as the guns all had equally as poor rates of fire.

In conclusion, the ISU-152 did not live up to its legendary name. Other Soviet field guns and tank destroyers had somewhat better results compared to the ISU-152, although the results were still not quite satisfactory.

Mythbusting: The 122 mm A-19S and D-25T / S were sufficient

It is a commonly held belief that the 122 mm D-25T / S and A-19S were sufficient at destroying the heaviest German armor. This belief is somewhat problematic, given the weight of the evidence.

According to a Wa Preuf 1 (a Wehrmacht weapons research facility) report from October 5th, 1944, the 122mm A-19 (the A-19S being used on the ISU-122, the latest Soviet SPG at that time) could not penetrate the upper glacis of a Panther. However, it could penetrate the lower glacis from a distance of up to 100 m, the mantlet from 500 m, and the side of the turret from 1500m. This was still somewhat wanting, as the Red Army would prefer to engage such tanks from longer ranges, to prevent heavy losses of their own tanks.

The improved 122mm D-25T (which was used on the IS-2, the D-25S was essentially the same, and was used on the ISU-122S) seems to have fared much better against German armor. Testing of the gun on the IS-2 platform in Kubinka in 1944 suggests that a King Tiger’s turret (likely the side) could be penetrated from up to 1000-1500m. The welds of front hull seams could also be penetrated from 500-600m. Whilst these penetration statistics might make the D-25T sound more promising, they must be taken with some caveats.

Firstly, to score such hits would require a very skilled and very experienced gunner – especially to score a hit on the turret from a range of up to 1500m. Secondly, similar to the ML-20S, the D-25T could only manage up to 3 rounds per minute. Thirdly, the validity of these statistics has been called into question, because they come from Soviet sources. In the past, these statistics were often exaggerated for propaganda purposes. Finally, the very fact that the ISU “BM” projects were put into production suggests that the Soviets knew that the D-25T would not give consistently reliable results in AT duties.

Whilst, indeed, the D-25T was, in theory, capable of destroying the heaviest German armor, it was perhaps not as reliable as it needed to be in the field. Of course, it is true that penetrations were not required to disable the tank or kill the crew (both in the case of the ML-20S and D-25T), but one could not simply rely on non-penetrating hits to, in some manner, disable the tank.

As a result of these relatively unsatisfactory Soviet AT capabilities against the Wehrmacht’s heaviest tanks, in June 1944, Zavod Nr. 100 began developing new, high velocity 122 mm, 130 mm, and 152 mm guns to be mounted on the ISU (and perhaps IS and KV) chassis.

Object 243 (ISU-122-1)

Object 243 (ISU-122-1) with the 122mm BL-9
Object 243 (ISU-122-1) with the 122 mm BL-9. This vehicle is distinguishable as its gun has no muzzle brake, and looks like an elongated A-19S. However, the gun replicator has been angled (see the rectangular plate on the mantlet below the gun), unlike a regular ISU-122.

  • The Object 243 featured the 122 mm BL-9 gun – one of the infamous BL guns made at OKB-172. The vehicle can be distinguished by its gun and mantlet. The gun essentially looked like a longer version of the A-19S. The mantlet also had some tweaking to fit the longer and heavier gun – most notably, the tip of the gun replicator has been angled to one side (just below the gun).
  • It could penetrate 204 mm of armor at 1000 m, with 2 rounds per minute.
  • The gun’s muzzle velocity was 950 m/s with an 11.9kg AP shell.
  • It had a range of 10,700 m, compared to the 6000 m range of the 152 mm ML-20S of the ISU-152 and SU-152.
  • It could carry 20 AP rounds, the same as the ISU-152.
  • Like the other “BM” guns, the BL-9 was likely too powerful for its mountings, which caused mechanical issues.

Object 246 (ISU-152-1)

Object 246 (ISU-152-1) with the 152 mm BL-8
Object 246 (ISU-152-1) with the 152 mm BL-8. This vehicle is distinguishable by its slightly longer gun than the Object 247 (15 cm, or 5.9 inches), but the same muzzle brake, and its unchanged gun replicator.

  • The Object 246 featured the 152 mm BL-8 gun. This vehicle can be distinguished by its distinctive muzzle brake, and unaltered gun replicator.
  • It could reportedly penetrate 203 mm of armor at 90 degrees from up to 2000 m away (dubious) 1, with 3 rounds per minute.
  • The gun had a muzzle velocity of 850 m/s with a 43.56 kg HE shell.
  • It had a maximum range of 18,500 m.
  • It could carry 21 rounds.
  • Whilst these results sound excellent, trials in December 1944 showed that the crew found operating the gun difficult, the muzzle brake and breech block were unreliable, and the barrel strength and angle of horizontal guidance were unsatisfactory. Consider also that the very long gun would limit the maneuverability of the vehicle, much like the D-25S on the ISU-122S limited its maneuverability. As a result, the 152mm BL-10 was developed…

Object 247/ISU-152-2 by David Bocquelet

Object 247 (ISU-152-2)

Object 247 (ISU-152-2) with the 152 mm BL-10
Object 247 (ISU-152-2) with the 152 mm BL-10. This vehicle is distinguishable by the length of its barrel (it was slightly shorter compared to the BL-8), its muzzle brake, and its altered gun replicator.

  • The Object 247 fitted the 152 mm BL-10 gun, an improvement of the BL-8. This vehicle can be distinguished by its muzzle brake and slightly altered gun mantlet, whereby the rectangular tip of the gun replicating system had been angled, unlike the original ISU mantlet.
  • It could penetrate 205 mm of armor from 1000 m.
  • The gun had a muzzle velocity of 851 m/s with a 43.56 kg HE shell.
  • It had a maximum range of 17,000 m.
  • It could carry 20 HE shells.
  • Testing revealed that barrel integrity and angle of horizontal guidance were poor.
  • It was eventually deemed that there was no need for this work to continue, mostly because the war was over, and there was no need to combat heavily armored German vehicles.
  • Consider also, that whilst the barrel length was a little shorter than the BL-8, it, too, would still suffer from maneuverability issues as a result.

Object 250 (ISU-130)

Object 250 (ISU-130) with the 130 mm S-26
Object 250 (ISU-130) with the 130 mm S-26. This vehicle is distinguishable by its unique muzzle brake.

  • The Object 250 (ISU-130) was built in autumn, 1944 and featured a 130 mm (5.12 in) S-26 gun. This gun is sometimes referred to as a naval gun, but this is not entirely accurate – the S-26 derived from a naval gun and featured a rectangular muzzle brake and horizontal wedges.
  • It could penetrate 196 mm of armor from 1000 m.
  • It had a muzzle velocity of 702 m/s, firing a 33.4kg HE shell, with 1.5-2.5 rounds per minute.
  • It had a range of 15,000 m.
  • It could carry 25 shells, which were smaller than 152mm shells, meaning that it provided similar ballistic results to the 152mm BM guns, but could carry more shells.
  • In October 1944, the ISU-130 underwent factory trials, and the following month, trials were held at the Polygon.
  • A major concern came from the caliber – 130mm. The issue was that the army would have to make special arrangements for the 130mm naval shells to be supplied to the army, and thus it was decided that a gun using current army-issue 122mm or 152mm would be preferable.
  • Testing of the ISU-130 ended in 1945, and the gun was sent to the TaSKB for completion, but the war was over, and the project was disbanded.
  • The ISU-130 is currently preserved at the Kubinka Tank Museum.

The ISU-130 preserved at Kubinka.
The ISU-130 preserved at Kubinka.

Object 251 (ISU-122-3)

Object 251 (ISU-122-3) with the 122 mm S-26-1.
Object 251 (ISU-122-3) with the 122 mm S-26-1. This vehicle is distinguishable by its round gun mantlet and its unique cylindrical muzzle brake.

  • The Object 251 was derived from the ISU-130. It featured essentially a 122 mm version of the 130 mm S-26, which was designated the S-26-1. It had a round muzzle brake, different components, but the mantlet was the same shape.
  • It could penetrate 204 mm of armor from 1000 m.
  • It had very similar ballistics to the BL-9, but had a muzzle velocity of 1000 m/s, firing a 25kg shell.
  • It could fire a disappointing 1.5-1.8 rounds per minute.
  • It underwent field tests in November 1944, but according to sources, something (probably the mantlet and / or gun mechanism), was simply not strong enough to withstand firing the gun.
  • The gun project was totally completed in June 1945, but was abandoned due to the war’s end.
  • (Note that the ISU-122-2 was the ISU-122S with the 122 mm D-25S, hence the skip from ISU-122-1 to ISU-122-3).


The “ISU High Powered Gun Projects” were, in many respects, a failure. True, the guns were incredibly potent, particularly in the case of the S-26-1, which could penetrate 204 mm from 1000 m. They also had a very long range, only limited by the elevation of the ISU mantlet. However, they were simply not practical and mechanically reliable enough for their intended purpose, which was to knock out the thickest armored Wehrmacht tanks consistently, and from long ranges.

Even if the vehicles were put into serial production, how often these tanks would face off with the most heavily armored vehicles of the Wehrmacht is questionable. With Jagdtigers, King Tigers, and Ferdinands being so rare, the war was more likely to have ended before the ISU High Powered Projects saw combat with the vehicles they were designed to destroy. What had ultimately put the nail in the coffin for these guns was that the war had ended, and they were no longer necessary.

Sidenote: Designations and identification through photos

In the writing of this article, it has been exceptionally difficult to pin down which photos correspond to which project. Indeed, some sources only mention four (in some cases, only three) High Powered Gun Project vehicles. It has been the author’s conclusion that there were five such High Powered Gun Projects mounted onto ISU chassis, as outlined in Solyankin’s book “Советские тяжелые самоходные артиллерийские установки 1941-45″. Most online sources, particularly non-Russian language sources, are incredibly inaccurate. Gun statistics were mostly provided by a Soviet data set as provided by Tankarchives.blogspot. However, these statistics sometimes differ with Solyankin.

12.8cm PaK 44 L/55
Object 243
Object 246
Object 247
Object 250
Object 251
ISU-152, SU-152
122 mm
152 mm
152 mm
130 mm
122 mm
152 mm
122 mm
128 mm
Penetration@90 deg
204 mm from 1000 m
157 mm from 1500 m
155 mm from 2000 m
203 mm1
from 2000 m (Dubious)
205 mm from 1000 m
202 mm from 1500 m
160 mm from 2000 m
196 mm from 1000 m
184 mm from 1500 m
156 mm from 2000 m
204 mm from 1000 m
157 mm from 1500 m
156 mm from 2000 m
125 mm from 500 m
147 mm from 500 m
138 mm from 1000 m
and 129 mm from 2000 m
200 mm from 1000 m
30 degree angle
PzGr.43 shell
Rounds per Minute
3 1
No data 1
1-3 2
(crew dependent)
1-3 2,3
(crew dependent)
Muzzle velocity
700 m/s (HE)
850 m/s (presumably HE) 1
826 m/s (AP)
851 m/s (HE)
898 m/s (AP)
702 m/s (HE)
1000 m/s (AP and HE)
600 m/s (HE)
800 m/s (HE)
950 m/s (AP)
10,700 m
18,500 m 1
17,000 m
15,000 m 1
15,000 m 1
6000 m
5000 m
24,410 m
Shell Weight and Type
11.9kg AP
43.56kg HE
43.56kg HE
33.4kg HE
25kg HE
43.56kg HE
25kg HE
28kg HE
28.3kg AP
Ammo Capacity
21 1
30 1, 3
Overall length, chassis included
11.15 m (36.58 ft)
11.82 m (38.78 ft)
11.67 m (38.29 ft)
11.42 m (37.47 ft)
11.26 m (36.94 ft)
9.18 m (30.12 ft)
9.85 m (32.32 ft)
10.65 m (34.94 ft)


1 – Note 1 – Most data has been obtained from this Soviet data set. However, certain statistics have not been given and have been obtained from alternative (potentially dubious) sources. Where necessary, statistics provided by Solyankin have been used, but these are questionable.

2 – Note 2 – Experienced crews were able to load much faster. Consider that the BM guns were likely tested by experts in test ground conditions, thus likely making their rounds per minute data higher than would be in the field, by more typical tank crews.

3 – Note 3 – Obtaining the ISU-122S’ ammo capacity has been difficult. It is reported that with a crew of four, instead of five (IE, one loader instead of two), then ammo capacity was increased, but the only given figure is 30, presumably with two loaders.

Germany’s Panther Tank: The Quest for Combat Supremacy”, by Thomas Jentz
Sturmgeschutz & Its Variants”, by Walter J. Spielberger
“Советские тяжелые самоходные артиллерийские установки 1941-45”, by A.G. Solyankin (second page)
tankarchives.blogspot (second page)
tankarchives.blogspot (third page) forums
WW2 AT Penetrations.pdf (second page)





56 thoughts on “ISU High Power Gun Projects

        1. That’s fine, but I don’t understand what you expect to achieve by contacting support about it. Unless your request is somehow escalated, nothing of worth would come out of it.


          1. I asked for help, i provided the evidence, provided them with valid feedback from other players, gave them valid reasons.

            I specifically asked them to do something about this problem.

            This guy could push this forward because you always have the choice of mailing the ticket to your superiors.

            Now i will ask Rita to say something if she goes to some kind of WG meetings.
            I won’t just sit back and cry and neither should others.

            Maybe it’s time we do something about this, and stop acting like we can’t do shit about it.

            If we step together and act as one then we can push this up their asses.

            Liked by 1 person

            1. btw… i know “Rita bla bla bla… ” well i know for a fact that they invite her.
              If others go there then they should also say something.


                  1. This is a trap question, I refuse to answer!

                    Well, I think currently, TAP is the better blog.
                    Mostly the same content is posted on both, sometimes one outpaces the other.
                    Rita has access to more information, TAP has access through more people on the actual blog.

                    Anyways, I go to both because it gets me more information and there’s usually different discussions on both. I know you are hellbent on having the better blog but idk where you want to go with it.


              1. Why are you praising someone who has days without posting any articles… Last time that person went to Cyprus to ask WG stuff it wasn’t interesting at all. That „blog” of hers declined in quality since its start, and cannot be compared to the predecessor.


                1. That’s why i switched to your blog more than 1 year back (i actually heard about it in the comment section of status report). Her posts frustrated me because they were (and as i can see still are) days outdated… things everybody already knew about and then she makes a post about that.

                  I didn’t even know what’s happening with her but i remembered she got invidet to some sort of WG interview… so i sent her a mail asking for help and i bookmarked her blog.

                  This is when everything went wrong on my side… i got lucky that you noticed my comment (or i don’t know what happened but thank you again) and you made a post about it.
                  So i press on the bookmark to check if there’s something new here and i see “clown camo tanks… thanks to 2goXD… etc etc)

                  I automatically assumed it was Rita who made the post (you must be aware of the similareties of your blogs… )

                  So yes this is the whole story on why i contacted her and why i thought she wrote the post.

                  So sorry for this inconvenience and again thank you for all your support Seb, i really appreciate it.

                  Cheers ;)


                1. I’m all up for change, but I have never seen any support team for any game do what you describe. Soviet, fixing technical bugs is one thing, asking a minimum wage WG EU support employee to singlehandedly convince the marketing team for you won’t work. If there is a way, I very much doubt doing it through regular support channel would yield results … but good on you for trying.


                  1. I contacted Rita, now i hope for the best.

                    I also posted this new topic:

                    I will do as much as i can to benefit both EU community and in fact also WG profit (sadly they are too stupid to realize that).

                    I expected WG support to throw this ticket but at least i tried and if they got 20 tickets of this type then maybe they would start asking themselves what’s going on.

                    I’m sure we can do this.


  1. And the relevance of that ticket to this article is… ?

    On topic: good find, STD. It’s always nice to read myth busting articles that state facts, not fiction or wishful thinking.

    Liked by 1 person

          1. oh sorry but this is just the comment section.
            What did you expect on the blog that circles around WG games ?

            And if you think everybody was as butthurt as you are then go visit this link

            Why do you have to jump from your chair and start fist fighting when you see a comment trying to fix a wot related problem ?!

            I wouldn’t say anything if i tried to sell vacum cleaners and rape you with some shitty piramidal system.


      1. Yes, there’s a lot of very interesting article on Internet, but sometimes I’m just too lazy to go look for them by myself. So thanks to you as well for bringing it here :)


  2. In a way it is pretty ironic that in game all those ISU “projects” have excellent guns in terms of dealing damage.

    It only shows that even developers themselves fell in that “myth” and that Russian bias in-game is real!

    Liked by 2 people

    1. Actually, they DID have the damage potential in reality too. Just read about the ISU-152, the ML-20 could knock out pretty much every vehicle in the world IF it hit (hell, it could probably even knock out an Abrams or a Merkava as well). The main problem was its accuracy (which is not surprising since it wasn’t designed as a TD, but as an assault gun – a completely different type of job, even if some assault guns did great as TDs). And, as anyone who played the SU/ISU-152 with the ML-20S can testify, it has exactly the same problem in-game – huge damage, mind numbing precision. While sometimes you can snapshot a moving LT on the other side of the map, most of the time you have to get up close and personal in order to do any damage So it’s pretty realistic in the game.

      Regarding the other guns (BL-10 etc), those were planned and their WoT performance is rather close to reality (as much as it can be in a game). Not to mention that they were actually tested on that very same platform, only that it couldn’t handle the stress of firing the gun AND it was unwieldy. But considering that many other historical vehicles in the game have unrealistic guns for the sake of balance (the 90 mm for the Hellcat, the 75 mm L70 for the StuG and so forth), adding the BL-10 to the ISU is not biased in any way. While there are some blatantly overpowered vehicles in the game (many, but not all Russian), the ISU is not one of them, it’s quite a nicely balanced vehicle that manages to be realistic too.

      However, the myth that this article DID bust was that the Russians relied on the ML-20S for anti-tank purposes. They did not. It was an improvisation, they knew it and they took steps to rectify it.


    1. Sorry, but that’s not me who wrote it :P

      It was by a friend of mine named Will, a really talented writer.

      As for a article about the Hellcat with a 90mm… I don’t know. I’ll take it into consideration. I’m about to post an article myself in a couple of days but that depends if I can figure out certain things that are a mystery! It’s been really bugging me.

      Liked by 1 person

  3. After reading this article the thought that half (if not more) of the things we see as stats for the Soviet tanks in the game are made up and utter shit. The only thing they were good at was making everything en-masse, anything else they worked on was crap or stolen.

    Makes me think of what the Third Reich could have done with the factories and resources of the Russians if they somehow managed to defeat them…


    1. In my opinion, it’s just the right guns on the wrong tanks. The ISU’s chassis was not suited for tank destroying. The ISU-152 was designed as a mobile artillery and an assault gun. It did it’s job decently. A whole new casemate should’ve been designed for it,


    1. I assumed it’s that thingy right below the barrel, but what do I know.
      It can be anything!

      *Zephyr thinks of the Replicators from Stargate SG1*


  4. Fully radish ! Your post its clearly pro-fascist one ! The ISU-152’s did just fine at battle of kursk ! Of he didn’t needed to be fire his HE from close distances… Its was just enough to fire from long distances… The HE did heavy losses of the crews. some times the Elephants was just fine without damage, but the hole crew was lost “concussion and spalling”!


    1. As the author of the original article, I can tell you right now that suggesting that I am “pro-fascist” because I present historical facts is beyond absurd. I am a historian, and thus I am not a partisan of any – Sorry, I got bored midway through this sentence because it shouldn’t even need saying.

      SU-152s and ISU-152s did fine at Kursk, but they did not inflict the biggest losses by far. One could fire from long ranges and still score a kill, but my entire point of the mythbusting section hinged on what happened in reality, not on paper. As I explained in the article, the vehicle was not at all suited to tank destroying. To reiterate, low velocity howitzers are not accurate enough, the ISU chassis did not have thick enough armour for such a role, and it had a sup-optimal rate of fire for the role of tank destroyer.

      Liked by 3 people

    2. Kursk was a German loss from the get go. Zhukov was a cleaver devil.

      This “…JEDI” one (George Lucas would rip off his beard if he knew how his characters are treated …) must be one of those donkeys who believe Crimea should be returned to Russia.

      Liked by 1 person

  5. ISU130 130mm S26 gun
    It could penetrate 196 mm of armor from 1000 m.
    In-game: 215mm pen at 100m

    ISU152 152mm BL-10
    It could penetrate 205 mm of armor from 1000 m.
    In-game: 286mm pen at 100m

    WG Logic !

    Liked by 1 person

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