Steve (BTS): ROF of ISU-152

[Skipper]

Of course, SU-100 was a better tank killer than SU-122 and SU-152. For a simple reason that the gun it carried was developed as an AT gun in 1944, and the whole thing is primarily a long range tank killer.

OTOH, SU-122 is a 122mm field howitzer on a tank chassis, developed for taking out fortified MG nests and such. They did have a HEAT round which could KO pretty much anything germans fielded during 1942, but due to a slow initial speed (it is a howitzer, after all) it was extremely difficult to hit anything with it from any but close distance.

Mattias:

The pictures are from http://armor.kiev.ua. It is all in russian, but it has a huge number of pictures like this, for a huge variety of armored vehicles from WWI till today.

[Skipper]

Oh, yes, all these SPGs (except SU-100) had a separated round and two loaders.

[rune]

Well, I do NOT know where you got those figures, but let's see what the people who used the 122mm have to say about the 122mm. All quotes are from the Russian Military Zone.

Further, after the first encounters of the IS-2 with German heavy tanks, it turned out that its pointed 122 mm AP round - the BR-471 - could only penetrate the frontal armour of a Panther within 600-700 metres. The less powerful frontal armour of a Tiger (the vertical armour of a Tiger, although thicker than that of a Panther, was more easily defeated by the pointed projectile of the Soviet gun, while it mostly ricocheted off the sloped armour of a Panther) could be penetrated from distances up to 1200 metres. However, at such distances only very well trained, experienced gunners could score a hit. The powerful HE round, OF-471, when fired at German tanks, caused cracking and even complete tearing off of the front armour plates at the welded seams. The first results of the use of the IS-2 in fighting conditions (backed by the results of its tests at the Kubinka testing grounds in January of 1944) forced designers to look for new solutions to its problems.

It was only after the Panther's armor went down in quality in 1944 that the HE round could cause holes or cracks in the armor. The Russian Military zone also had this to say about firing rate:

After this, it produced only the IS-122 with the new 122 mm gun D-25T with a wedge-shaped semi-automatic breech, which allowed an increased rate of fire from 1-1.5 shots per minute to 1.5-2 shots per minute

Rune

<BLOCKQUOTE>quote:</font><HR>Originally posted by Amedeo:

Fow what concernes the relative performances of the 100mm, 122mm, and 152mm Soviet guns, well actually the 100mm had superior armour piercing performances _against vertical armour_ but the blunt nose 122mm APBC round fared better against sloped armour being able to rip trough the Panther frontal glacis at 2000m, while the 100mm could have performed better against the Tiger. Anyway to have guns able to frontally destroy Panthers and Tigers at medium/long ranges is a dream in CMBO terms. The problem is to hit them!

Regards,

Amedeo<HR></BLOCKQUOTE>

[Skipper]

Rune, what I am saying does not contradict what your quote is saying. Here's why:

> Further, after the first encounters of the

> IS-2 with German heavy tanks, it turned

> out that its pointed 122 mm AP round - the

> BR-471 - could only penetrate the frontal

> armour of a Panther within 600-700 metres.

SU-122 that I was talking about was armed not with D25T gun, but with M-30 howitzer. The latter had no AP round at all (for apparent reasons). Hollow charge round for it was produced from May 1943. Btw, there is at least one known german account of a Tiger KO'd by SU-122 earlier than that - multiple HE (plain HE, not HC) hits.

> After this, it produced only the IS-122

> with the new 122 mm gun D-25T with a wedge-

> shaped semi-automatic breech, which

> allowed an increased rate of fire from 1-

> 1.5 shots per minute to 1.5-2 shots per

> minute

IS-122 was a tank. We were talking about self propelled guns. The key difference was tha SPGs had two loaders, whereas IS-122 had only one. I think, that's where most of the confusion is coming from.

[ 06-04-2001: Message edited by: Skipper ]

[Amedeo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rune:

Well, I do NOT know where you got those figures, but let's see what the people who used the 122mm have to say about the 122mm. All quotes are from the Russian Military Zone. [...]

<HR></BLOCKQUOTE>

What you quoted from the RMZ is absolutely correct but does not contradict what I wrote since I was referring to the blunt nose 122mm APBC round, that is the BR-471B, different from the plain AP round (sharp tip w/o ballistic cap) referred in your quote.

The performances of the BR-471B were analyzed bu the US Army that managed to put its hand on an abandoned IS-2 in Germany. While the performances of the BR-471B were not very different from the vanilla AP against vertical armour they found that its performances against sloped armour were impressive (owing to the blunt nose that caused the round to point downward and go through a path shorter than straight-on LOS). Rexford will surely be able to provide more accurate data (he has the US reports).

It's also worth noting that this is in accordance with what you can find on the excellent RMZ in the documents dealing with the decision to adopt the 122mm or 100mm gun on the IS tanks and the one describing Kubinka tests with 122mm, 100mm, and 88mm (L71, German) against captured Panthers.

Regards,

Amedeo

[Amedeo]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Triumvir:

As far as I know, the only M1 disabled by enemy action (as opposed to mines) in the Persian Gulf was hit by a D-10 in the rear. Anyone have more information on that?<HR></BLOCKQUOTE>

IIRC it was actually hit by an HEAT round fired by a 73mm low pressure gun mounted on a BMP-1.

Amedeo

[ASL Veteran]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Skipper:

IS-122 was a tank. We were talking about self propelled guns. The key difference was tha SPGs had two loaders, whereas IS-122 had only one. I think, that's where most of the confusion is coming from.

[ 06-04-2001: Message edited by: Skipper ][/QB]<HR></BLOCKQUOTE>

The IS-122 was a self propelled gun. Perhaps you are thinking of the IS-2? I have some printed sources at home that also state a ROF of between 1 and 2 per minute. Sorry, can't cite them right at the moment though.

[Triumvir]

ASL,

the IS-122 is a tank. The ISU-122 and SU-122 were SPGs, but the IS-122 was a tank the same way the IS-85 was a tank. We know them better as the IS-2 and the IS-1 respectively.

The site referenced at vif.ru makes that pretty clear, and added another nugget to my storehouse of useless information... 8)

[Commissar]

<BLOCKQUOTE>quote:</font><HR>Originally posted by ASL Veteran:

The IS-122 was a self propelled gun. Perhaps you are thinking of the IS-2? I have some printed sources at home that also state a ROF of between 1 and 2 per minute. Sorry, can't cite them right at the moment though.<HR></BLOCKQUOTE>

IS-122 was the name of the IS-2 during trials and development. There were two IS tanks, the IS-85 (which carried the 85mm) and the IS-122 (which carried the 122mm). The names were eventually changed to IS-1 and IS-2 respectively. The assault gun versions built on the IS chassis were designated ISU. If you are taking about the 122mm IS-based assault gun, you're talking about the ISU-122 and not the IS-122 (which is nothing more than the IS-2's previous designation).

The 100mm indeed had superior AP performance compared to the 85 and 122mm. However, the gun and ammo were new and not many of them were available. The Soviets therefore chose the 122 because it and its ammo were plentiful and still maintained excellent HE capability and good AP ability, although still inferior to the 100mm.

[ 06-04-2001: Message edited by: Commissar ]

[Skipper]

> I have some printed sources at home that

> also state a ROF of between 1 and 2 per

> minute.

For the tank(IS-2 or IS-122), yes. For the SPG on same chassis with same gun (ISU-122) - no, owing to the second loader and much bigger combat compartment (superstructure).

[ 06-04-2001: Message edited by: Skipper ]

[ASL Veteran]

I stand corrected . Oh, all that Soviet armor looks alike anyway . The ROF that my source has specifies the ROF for both the tank and the SP gun as being between 1 and 2 IIRC, but I would need to look at it again. Could possibly be 2 - 3 for the SP gun I suppose.

[Commissar]

ASL Veteran:

Do they still sell ASL these days?

[Wolfe]

It's mostly been answered, but just to check whether I have it right, here is my list of the various AFVs discussed:

Tanks

IS-1 (IS-85) - 85mm D-5 gun on IS chassis

IS-2 (IS-122) - 122mm D-25 gun on IS chassis

IS-3 - IS-2 with a different turret

Tank Destroyers

SU-76 - unknown 76mm gun on T70 chassis

SU-76M - 76mm F-34 gun on T70 chassis

SU-85 - 85mm D-5 gun on T34 chassis

SU-100 - 100mm D-10 gun on T34 chassis

Assault Guns

SU-76p - 76mm L-10 gun on T26 chassis

SU-76i - 76mm F-34 gun on captured PzIII chassis

SU-122 - 122mm M-30 howitzer on T34 chassis

SG-122A - 122mm M-30 howitzer on captured PzIII chassis

ISU-122 - 122mm D-25 gun on IS chassis

SU-152 - 152mm ML-20 howitzer on KV chassis

ISU-152 - 152mm ML-20 howitzer on IS chassis

Hope that helps. And hope it's correct.

And a few questions. What gun is on the SU-76? Is the 76mm F-32 gun mounted on any vehicle? Is the 85mm gun on the KV-85 the same as the one on the IS-1?

This stuff can be real confusing. I really hope BTS tries to identify the gun mounted on each AFV in the stats window. Inquiring minds want to know.

Thanks for any help.

Sources:

Red Steel

Russian Military Zone

Wargamer Weapons data

Red Army Handbook - Zaloga

Encyclopedia of Weapons of WWII - Bishop

- Chris

[Amedeo]

The gun on the SU-76 was the long barrelled divisional gun 76mm ZiS-3 (IIRC) gun. Much better than the shorter 76mm ones in the T-34 and KV-1. Ditto for the SU-76M.

Moreover the IS-3 is not simply IS-2 with a different turret. It had also a very different hull much better protected. The IS-2 itself had different styles of hull front protection during the war.

Regards,

Amedeo

[ASL Veteran]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Commissar:

ASL Veteran:

Do they still sell ASL these days?<HR></BLOCKQUOTE>

I believe it is still sold by Multi Man Publishing. It is probably pretty hard to find though. They are going to come out with a new module for the Axis Minors and another smaller module dedicated to the Finns (don't know why they get preferential treatment)

[Skipper]

SU-76M had ZIS-3 gun as well.

Only 170 original SU-76s were produced, and after "trial by fire" this design was modified to SU-76M, which became the second largest AFV manufacturing program in USSR after T-34.

There was also ZIS-30 SPG with 57mm ZIS-2 gun, about a hundred produced.

[JasonC]

I second Amedeo on the SU-76. It was the M-1942 ZiS-3, the divisional duel-purpose gun used in the artillery regiments and also used as an anti-tank gun. Which is an L54 piece, slightly longer than the German PAK 40 but basically the same size, for comparison. The same weapon was also used by the Germans on the 76.2mm Marders, using captured pieces. Indeed, an SU-76 is basically a Marder.

The primary change with the "M" model in summer of 1943 was standardizing the chassis and improving the engine layout. The gun was the same. Before then they were less reliable mechanically, and few were built because of it. The "M" model was based on the successful T-70 tank chassis and essentially had worked out the bugs, that is the main difference. It was thus mass produced on a scale of 10,000s, whereas only 1000 or so were made before the "M" model.

On the ISU-152, I can explain several issues in doubt about the layout and crew roles. The second loader was on the rear of the commander's, right side of the vehicle. His jobs were loading the powder behind the shell, ramming, and closing the breech. The first loader, on the left behind the gunner, opened the breech and loaded the actual shell ahead of the powder charge.

The ammo was on racks along the sides of the vehicle, two deep from the wall, five high. On the left there were two racks for the actual shells, 10 each. Generally one was AP and the other HE. All readily accessible. The gun is off-center toward the right side, and the space on the right is therefore more cramped. The commander is out of the way above the gun, basically, but the right side assistant loader has less room, with the recoil space of the gun taken into account, etc. Because of that, there was only one rack for powder charges on the right, 10 of them. Ten more charges were stored either under the gun position in a floor compartment, or a couple ahead of the powder rack on the wall benches where the assistant loader sat while traveling, then used first.

The powder charges were interchangeable for AP or HE of course. So the layout would allow ~12 shots rapidly, then a bit more time needed before the next 8. If the crew threw safety to the wind or when firing indirect as artillery, I'll bet they fished out the powder and stacked it on the floor, or piled it high on the bench on the right. We did similar things when stationary, firing "in battery", with the M-109s. You wouldn't want to do that when traveling, though, only in position.

I have also seen yet another source confirm that in practice the gun could be fired 3-4 times per minute, which is what I would expect when pushing. It is at a site covering the interior of this beastie, at this URL -

http://www.kithobbyist.com/AFVInteriors/isu152/isu152a.html

See the text accompanying picture 7. Incidentally, that breech looks just like the one on the M-109, in terms of the threaded breech-block, the way it swings clear, the lever handle to make moving the heavy breech mechanically easier, etc. The only possible difference is the M-109 spring-release to close the breech most of the way without manual effort. But this one would not be hard to operate.

As for ammo on the M-109, its ready racks are at the rear of the vehicle, and one loader fetches them all. In action, the shells are often placed on the floor at the left rear, and powder is often cut (and shells fused, an artillery complication) by crewmembers from the ammo vehicle and handed in the back of the vehicle. Shell prep therefore goes on in parallel with loading and firing, for more sustained shooting. For short "hip shoots" right after pulling into a position, it is all run out by the loader from what he has prepped in the ready racks. And the same 3-4 round ROF is easily achieved. Understand that in either case, one is talking about a peak ROF for a period of 2-4 minutes. Which is what would matter in close action, almost always, and is also the size of typical fire missions when acting as indirect artillery.

I think 2 rpm would be a "green" rate, with 4 possible for veterans, and 3 regular. I don't believe the 3 per 2 minute figure any more than I believe the field manual's 4 per 3 minutes for the M-109, which is after all the same number practically. For safety, done in a deliberate manner, or sustained, that figure is probably realistic. In action, or even just pushing to finish a mission fast in training, 3 rpm is easy, and would be with this layout too.

[Roksovkiy]

The true performance of the russian guns were quite poor compared to UK,US and German guns of comparable diameter.

Values at 0@ armour plate using APBC & APCBC

500M 1000M 1500M 2000M

ISU- 152mm 106mm 102mm 98mm 95mm

IS-2 122D-25 128mm 120mm 109mm 105mm

SU- 100mm D-10 135mm 129mm 120mm 100mm

German

88L71 185mm 165mm 148mm 132mm

75L70 124mm 111mm 99mm 89mm

US

90L53 M3 129mm 122mm 114mm 106mm

UK

17lb 140mm 130mm 120mm 111mm

The 152mm and 122mm russian guns were modified artillery and designed as valera shows against anti-infantry targets due to the rarity of german tanks from 1944.

The 152mm, 122mm and 100mm guns could not penetrate the front of the Elephant or Tiger II from any range. Many photos taken show dents on the front plates from these projectiles, other than that no damage was caused. The only gun that could theoretically penetrate a Tiger II was the british 17lb using special APDS ammo.

US reports of captured russian armour state that its cast and RHA armour was upto 50% less effective than german armour. The soviet quality controll methods were far less than wersertn standards, but they compenstated for this by the sheer number of tanks produced.

[ASL Veteran]

Interesting data Jason - someone in another thread regarding ROF mentioned that the Panther could achieve a ROF of 20 RPM in the French tests at Isigny (?). Do you feel that CM should increase the Panther's ROF to 20 considering it could acheive that ROF in a tight spot? I also seem to recall that Ian Hogg mentioned that the Pak 43 had to be kept below 20 RPM or the barrel would shake! :eek: Perhaps all ROFs should be increased in CM?

[JasonC]

No, I don't think all ROF need to be boosted. I think the tech grogs are too focused on imaginary differences between one big hulking rifle and the next one, whereas in reality practical ROF has more to do with very similar crews and human working speeds than they suspect. I think the ROF -range- is narrower, not the whole thing bumped higher.

Of course the guns with single-loading ammo have higher ROF, and ones with very light "one handed" shells (like 37mm and such) higher again. And the spread by crew quality might be a bit more, like +/- 25% for green or veteran compared to regular. But much of that is already in CM and I think close to correct.

Shell weight just doesn't matter very much, up to 155mm. There is a reason common field pieces stop around that size. The reason is that a 100 lb shell can be manhandled rapidly by one man, working hard to be sure, but working rapidly. Go up to 8 inch guns and the shells weigh 200 lbs and that is no longer true. As in Monty Python, "it is a simple question of weight ratios", shell to man.

Howitzer size weapons fire more slowly because of seperate loading ammunition, ramming of shells, and a more involved loading procedure overall. But that "slower" is on the order of 3-4 rounds per minute. Medium sized shells that it takes two hands to lift, but which load in one piece by a simpler procedure, can double that ROF, and there is precious little difference in firing time for one of them compared to another. Shells that can be handled in one hand and fired nearly like rifle cartridges in a bolt action, can add another 3-4 rounds per minute on top of that.

Until you get up to shells too heavy for a man to lift on the one hand, or down to semi-automatic loading on the other hand, there just isn't that much difference, because the human task just isn't that much different. Seperate loading is twice as long as the medium rate, and one handed is less than twice as fast as that medium rate, maybe half again as fast.

That is it. People want to read dramatic tech-dominance implications into tech-spec minutae beyond that, simply because they worship at the shrine of tech-spec minutae groghood, and it is in a manual somewhere. The human reality of loading and firing artillery pieces just doesn't vary that much, with liftable shells loading one at a time, that is.

[Freak]

To throw my $0.02 in, if the weight of the ISU-152 shell is 100 pounds, well, that is pretty heavy. I was just thinking though, could we somehow compare this Shell and or ROF to the 128mm gun in the JagdTiger?

[Michael Emrys]

Thanks, Roksovkiy, and others. That was the information I was looking for. So I suppose that in the end the comparison between the SU-100 and ISU-122 is: it depends.

Michael

[Commissar]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Roksovkiy:

The true performance of the russian guns were quite poor compared to UK,US and German guns of comparable diameter.

Values at 0@ armour plate using APBC & APCBC

500M 1000M 1500M 2000M

ISU- 152mm 106mm 102mm 98mm 95mm

IS-2 122D-25 128mm 120mm 109mm 105mm

SU- 100mm D-10 135mm 129mm 120mm 100mm

German

88L71 185mm 165mm 148mm 132mm

75L70 124mm 111mm 99mm 89mm

US

90L53 M3 129mm 122mm 114mm 106mm

UK

17lb 140mm 130mm 120mm 111mm

The 152mm and 122mm russian guns were modified artillery and designed as valera shows against anti-infantry targets due to the rarity of german tanks from 1944.

The 152mm, 122mm and 100mm guns could not penetrate the front of the Elephant or Tiger II from any range. Many photos taken show dents on the front plates from these projectiles, other than that no damage was caused. The only gun that could theoretically penetrate a Tiger II was the british 17lb using special APDS ammo.

US reports of captured russian armour state that its cast and RHA armour was upto 50% less effective than german armour. The soviet quality controll methods were far less than wersertn standards, but they compenstated for this by the sheer number of tanks produced.<HR></BLOCKQUOTE>

I think you may want to head over to the Russian BAttlefield. There are various AAR by Soviets units that have taken out Ferdinands (although they may have mistaken StuGs for Ferdinands) and Tiger 2s as well. I'm not sure if they were frontal shots but these German armor units do not appear to be the uber weapons as popularly believed. From

The Russian Battlefield--The IS-2 in Comparison with Its German Counterparts :

In August 1944, new German tanks appeared on the Eastern Front: King (Koenig) Tigers. Weighing 68 tons, this tank was larger and much heavier than the IS-2.

The first engagement of Soviet tanks with King Tigers did not favor the Germans; on August 13 of 1944 a company of IS-2 tanks (the 3rd Battalion of the 71st Guards Heavy Tank Regiment) commanded 1st Lieutenant Klimenkov engaged in close combat with German tanks, knocked out one King Tiger and burnt another King Tiger. About at the same time, a single IS-2 of the 1st Lieutenant Udalov ambushed 7 King Tigers, knocked out one of them and burnt another one. Survived five German tanks attempted to retreat but Udalov made a maneuver and destroyed third King Tiger. Four other tanks flee in panic. Details of that battle are here.

Anyway, engagements between IS-2's and King Tigers were rare because the Germans seldom used them on the Eastern Front. On 12 November 1944, not far from Budapest, a skirmish occurred between IS-2's and King Tigers of the 503rd PzAbt. Both sides lost several tanks. On January 12, 1945, a column of King Tigers of the 524th PzAbt engaged in close combat with IS-2's (near Lisuv). In the fierce battle both sides had heavy losses.

It is not fair to compare the IS-2 and King Tiger because of the large disparity in weight - more than 20 tons! It would be better to classify the King Tiger as a super-heavy tank. It had thicker armor and its 88 KwK gun was slightly superior in AP ability, though inferior in HE ability.

Many times I noticed some individuals tried to compare armor penetration values of the 8,8-cm KwK 43 and the 122-mm D-25T. Unfortunately, these individuals paid no attention on different nature of those values: they were calculated by different methods. In short, the difference of calculation was about 25%. Therefore, it would be better to either increase Soviet figures on 25% or decrease German figures. Of course, the result would be very approximate, but it is much better then direct comparison.

The reliability of the King Tiger was poor, especially of first series, this is clearly stated in the follow report. The rate of fire of the King Tiger was definitely higher, ammo load was also larger. From the other side, the mobility of the IS-2 was much better. Further, the IS-2 was much cheaper than the King Tiger, which is also a very important consideration.

---Actually if you could get Valera to discuss this with you it would be great. It would be good also because he is on the CM2 beta team. German armor quality also deterioated as the war lengthened so Russian penetration ability improved without them having to do anything. Apparently even an HE round from a 122mm from an IS-2 could and did cause great gashes and cracks in German armor. However, the Soviet's use of higher and higher caliber rounds may indeed have been to make up for inferior performance against other gun calibers.

[Matthew_Ridgeway]

Great posts Jason C...the only ones on this thread I bothered reading all the way through.

[Freak]

Nevermind.

[ 06-04-2001: Message edited by: Freak ]