Why was the 122mm gun chosen for the IS-2 ?

Instead of the 100mm gun which had superiour penetration power to the 122mm.

I remember reading somewhere, and I don´t know if this is true or not but it might give an indication answer, that tests were carried out by the Soviets comparing the German 88mm to the Soviet 100mm and 122mm guns. They used a captured Panther as the target. At a specific range the 88mm failed to penetrate the frontal armour of the Panther. The 100mm successfully penetrated at the same range, but the 122mm failed to penetrate. It ripped the glacis plate off instead.

 

I don't know, it's an interesting question. Maybe the 100mm wasn't provided with a decent HE round, like many good AT guns of the war, and the Soviets valued that too much. At least you're certain of a good HE punch with the 122mm...

 

I'm not sure of the exact calibers,but many guns were used over others simply because factories were already tooled up to produce them.Early model Churchills were efftcted by this as well.

 

It might also be that the sheer size of the gun impressed Stalin, especially since no other army had one that large mounted on a tank at that time. And the final decision on which gun to use would have been his.

 

Hello.
Some information from "Soviet Heavy Tanks"of Steven J. Zagola and James Grandsen Osprey-Vanguard N°24.

 

Thanks Patrice,

Who can argue with that !

 

We were both right then. It was about HE round capacity and about production facilities.

 

But maybe later the Soviets realised that the A-19 122 mm gun wasn't a good choice for their tanks, as the T-54 featured a 100 mm gun (I dont know if the one planned for the IS-2, but definitely not the A-19). Maybe after the war the production priorities changed, as well as the things tanks were supposed to do.
As far as I know, the IS-2 tank was supposed to engage soft targets, and thus they chose the 122 mm tanks that had great HE power. How did the 100 mm gun performed with HE rounds?

 

Skua - who says the 100mm out penetrated the 122mm?

Sov 100 L46 APCBC 130 120 110 100 95
Sov 122 L43APCBC 140 130 120 110 100

It is close but the 122mm is superior in AP, and much superior in HE. Little wonder why the choice was made.

(Source is Bovington - the one I gave you in PM).

:smok:

 

Aren't we getting confused with the 100mm guns?

Are they talking about the 100mm D-10 gun as fitted to the SU-100 or the more powerful 100mm BS-3 which was also an anti tank gun but never actually fitted to any tank?

 

I was thinking about the BS-3 100mm which was discarded in favour of the A-19 122mm for the IS-2. The IS-2 was, however, later equipped with the more powerful D-25 122mm gun. I don´t know how the latter compares with the BS-3 though.

 

In that case then YES Skua that was a better anti tank gun and a better all round gun than the IS-2's 122mm. No doubt about it. It had ample HE too.

It was just a shortage of 100mm barrel material and machinery that led the the IS-2 having the 122mm and not the 100mm BS-3. No other reason.

 

By the way, here's two very badly scanned pictures of the Su-100 from the museum at Poteau, Belgium.

 

Nice pics Roel. I always liked the SU 100 and SU 85. Great TDs!!

 

You're welcome! I really like the lines of those TDs, too. Except that I can't understand the SU-85, in that they put a gun in a turretless TD that could have fitted the same chassis in a turret. Usually the turret is remove in order to facilitate a larger gun without blasting off the moorings with the recoil (i.e. the SU-100).

 

Well Roel, by the time the SU 85 first appeared in combat the T34/85 didn't exist so the SU 85 DID have a bigger gun than any T34 at the time.

I believe the SU 85 first appeared in September 1943 whereas the T34/85 did not make it's first appearence until Feb/March 1944 so the SU 85 was actually in combat some 5 or 6 months before the T34 got an 85mm gun.

I don't know why it took them so long to upgrade the SU 85 to the SU 100 though. It wasn't until the end of 1944 that the SU 100s were appearing. Strange.

 

Ease of production?
I suppose the Soviets just wanted/needed weight of numbers, so got them.

 

I think someone said here in this forum that it was as expensive to build three turretless tanks than build two tanks with turret.

 

Probably, but the Russians nevertheless built those two tanks with a turret. These comparisons apply mostly to Germany.

 

Hi Skua

Im sorry but that is russian propoganda("Unless your talking about the 88mm L/56 gun").... Like these tests at Aberdeen USA show.

These tests are done against the same type of Steel(RHS) at the same Angle:

100mm L/52 using APCBC against 0* angle: 500m=211mm / 1000m=185mm / 1500m=161mm / 2000m=141mm..

88mm L/71 using APCBC against 0* angle: 500m=219mm / 1000m=204mm / 1500m=190mm / 2000m=176mm..

100mm L/52 using APCBC against 30* angle: 500m=170mm / 1000m=149mm / 1500m=131mm / 2000m=115mm..

88mm L/71 using APCBC against 30* angle: 500m=185mm / 1000m=165mm / 1500m=153mm / 2000m=143mm..

So as you can see the 88mm L/71 is by far the most powerful...
I didnt list the 122mm L/43 gun on the IS-2 but i can if you want me to..
The russian 122mm Was infact better against highly sloped armor than the 100mm L/52 gun, mostly because of its shells low agle hits on sloped armor.

One thing to be considderet when comparing Russian and German guns:

The russian test plates would max reach 350BHN in hardness, Whereas German test plates would reach 465BHN...

The normal test plate hardness for russia was 250BHN.
Germany's normal test plate hardness was 300BHN...

Sources: "WWII Ballistics Armor and gunnery by Lorrin Rexford Bird/Robert Livingstone" and "KingTiger heavy tank 1942-45 by Tom jentz and peter sarson"...and Online conversion's site offcourse...

All the best, KBO