IIRC they were great vs fortifications and infantry but had limitations vs tanks. Deadly when they hit but hitting was difficult due to problems with optics, slow ammo loading, and limited ammo supply. Generally hard to knock out although earlier models had problems with brittle armour and shot traps.

Hmm, thats interesting (although I can't say I'm really surprised), I guess the JS-2 suffered from some of the same problems faced by the the JSU-152 and some other large-calibre assault guns in terms of ammo and accuracy. Now in terms of ammo loading and supply, how does the 122mm JS2 rounds compare to the 128mm rounds employed by the German Jagdtigers, or even currrent the 120mm rounds employed by M1s and Leopard IIs? I'd imagine that (at the very least) the M1s could carry more ammo but how does the weight (per round) compare?

Someone must have recognised the problems with turret cohesion & layout in KV-1
...

Interestingly, the soviet were already building prototypes of the T-34M, with 3 man turret and tosion bars suspenssion as the war broke. The inspiration was a Pz-III they evaluated pre-war.
The development was abandoned due "major force reasons", but it prefigured the T-44.

The IS-2 had separated ammo loading.
What i find interesting is that the Soviets evaluated the posibility of installing 100mm guns (as the one in the SU-100), but found it unnecesary. Tough the 100mm was single shot, the rate of fire was only marginally better, and the ammo load increased very little.
Also, tough on paper the 100mm had better penetration figures, the 122 behaved better against the german heavies of the day (something to do with overmatching, armour technology and slopes). And off couse, the 122 had more HE bang in it, a fundamental thing for a breaktrough tank as they devised it. Poking a hole in the enemy front lines, for the T-34 to pour into.

The 122mm gun was chosen for JS-2 because barrels and shells were available in quantity. The only 100mm gun at the time was a Navy piece that did not have existing facilities to manufacture in large quantities.

If they had gone with the 100mm gun, they would have had to switch to 122mm pretty soon anyway, just as JSU-122 was born because the Sovs ran out of 152mm barrels for JSU-152. Apparently one thing the Sov factories were never short of was 122mm tubes and shells.

Also, tough on paper the 100mm had better penetration figures, the 122 behaved better against the german heavies of the day (something to do with overmatching, armour technology and slopes). And off couse, the 122 had more HE bang in it, a fundamental thing for a breaktrough tank as they devised it. Poking a hole in the enemy front lines, for the T-34 to pour into.

One of it's shells carried 25 kg of HE to the Panther's 7 kg. 
Matt

Are you sure that's kilos and not pounds Matt?  These are huge kilo figures for their respective calibres.

I recalled reading that it had a nasty weak point in the driver's hatch, which can be penetrated by medium AT guns. I was surprise the Soviets didnt remove the driver's hatch completely.

snip...
Beyond that, it actually would fare well against a Panther front to front.  According to German manuals, a Panther needed to be 600 meters to penetrate a IS-2 from the front while a IS-2 could penentrate the Panther at 1000 meters. ......  snip..
snip...
Matt

3) Front armor on late-war IS-2s was 90mm rolled or 100mm cast at 60 degrees, not 120mm. More than enough in any case... 

Are you sure that's kilos and not pounds Matt?  These are huge kilo figures for their respective calibres.

The fibel manuals do not compare penetration objectively, IIRC.

The wording is like " the JSII can be  dangerous to you beginning from 1000meters " . " You can be certain of KO damage to him at 600 meters " .

Other than that the  P IV / JS II encounters are mentionable in that the P IV didn´t always get clobbered.

Regards

2) IS-2 had perfectly fine optics, copied from a German Tzf-5 if memory serves, and with adequate-quality optic glass. The problem was that it was initially too close to the gun and the massive muzzle brake restricted vision.

Is that the lower or upper front hull?  I always read that the upper front hull was 120mm, but the lower front was 100mm...

Is that the lower or upper front hull?

The JS-II frontal turret armor equivalent is 120mm, but it was an 80mm plate at 60 or so degrees. The hull equivalent is 60mm at 60 degrees equivalent to a 80mm plate.

It seems their armor piercing rounds were not as good

There are no records or photographs to prove that the Tiger II's frontal armor was ever penetrated in combat.

Hmm... It would appear Herr Korner destroyed about 10% of what we lost in entire Berlin operation Pity he "withdrew" and had nothing but the word of a Teuton Knight to back his claim 

Hmm... It would appear Herr Korner destroyed about 10% of what we lost in entire Berlin operation Pity he "withdrew" and had nothing but the word of a Teuton Knight to back his claim 
Indeed. King Tiger was definitely a very tough target when it got lucky to break down in a good firing position

Although photos from Kubinka trials show that front turret *is* vulnerable to multiple 122mm hits, after 3 impacts it's in a pretty pitiful shape... so it is possible that even though no evidence exists this did occur.

Frankly I like the JSII.  A tank has 2 roles and killing other tanks is 1.  The JSII, unlike the Tiger II, had very useful HE.  Doubles the value of the tank.  I say it again and again, it wasn't Tiger versus allied tank.  It was much more commonly German infantry against allied tank as the Germans focused on small numbers of expensive tanks.

Not to mention tha fact that Tiger II weighted 68 tons while JS-2 weighted 46 tons. 

Although photos from Kubinka trials show that front turret *is* vulnerable to multiple 122mm hits, after 3 impacts it's in a pretty pitiful shape... so it is possible that even though no evidence exists this did occur.

Especially if the mantlet is removed along with the gun and the 88 fired back at the front turret.

I couldn't decypher this, can you elaborate a bit what you meant?

The 88mm gun along with its mantlet were removed from the captured Tiger II before test firing guns at the front of the turret.

how does the 122mm JS2 rounds compare to the 128mm rounds employed by the German Jagdtigers, <snip> but how does the weight (per round) compare?

Before the battle that nearly took my life, we were informed of a new Russian tank, the Josef Stalin III, that weighed forty-six tons and fired 122 mm projectiles. Because of its thick (120 mm), sloping armor, our 75 mm rounds would simply bounce off its skin unless we hit it from the side at a very close range. When I fired at the T-34 in the valley, I wasn't aware that there were a number of those monsters waiting two kilometers away at the edge of the forest. No sooner had I pulled the trigger than the Russian behemoth began firing. For once, the Russians struck our tank with their first round. The projectile hit our vehicle between the barrel and the barrel sleeve of our cannon. It tore our cannon off where it struck and, incredibly, entered the exposed chamber where it detonated, causing our loaded round to detonate as well. This tremendous explosion caused our waiting rounds, though not the magazine, to instantly explode as well. Eyewitnesses stated that our welded assault gun's armored roof was propelled from its position by a sheet of flame that rose about 100 meters into the air. I am sure this must have been an exaggeration, the force necessary to wrench that massive steel roof away from our tank and fling it through the air had to be considerable. Apparently, my training in mounting and dismounting in Bamberg as well as in Rastenburg paid off for I must have subconsciously crawled off the tank and sought cover behind it. Since our assault gun was totally destroyed and our crew miraculously lived through the ordeal, it became known as the "Miracle Tank of the Eastern Front." Our driver, who had survived the incident relatively unscathed, would not talk for five days.

My fourth and final wound occurred on August 8, 1944 on a beautiful summer day about two miles south of Raseinen, Lithuania. Our tank was detailed to investigate, as the lead tank of the Company, the activities of the Russians in the vicinity of Raseinen. As we pulled up behind some bushes on a hill, I spotted a Russian T-34 tank diagonally crossing the valley in front of us. I had fired my first shot at the Russian tank when, at that instant, I sensed a shiny object approach our tank at a tremendous speed from the direction of eleven o'clock. Describing the event takes time, but this was an instantaneous occurrence. All I knew that danger was approaching and before I could shout, "Aufpassen!" (watch out!), there was a bright flash and then nothing - no sound no following explosion. I subconsciously crawled out of the tank.

I regained consciousness when kneeling on the ground behind the tank. I saw my driver, also kneeling, in front of me. "What happened?", I asked him and he replied, "We got hit!" When I asked him where the other members of our crew were he replied, "They are dead." As the tank engine finally sputtered and died, I heard a moaning and told the driver, "I think one of them is alive, let's help." As we both leapt up onto the rear of the tank, we found the loader alive but he had a gun in his hand and was preparing to shoot himself. This was often the reaction of a tank crew member who, when his tank was hit and he seemed unable to exit the vehicle, he preferred to commit suicide rather than go through the agony of slowly burning to death or to be captured by the Russians. I immediately knocked the weapon out of his hand and told the driver, "Help me pull him out." We tried but found that we could not budge him for there was considerable debris throughout the tank's interior which had his legs trapped. At that moment, we heard our commander begin to moan. We moved over to the left side of the tank where we found him as securely caught in the wreckage as the loader. At that moment, Russian machine gun fire began strafing our disabled vehicle so, following our trained reactions, we jumped off the tank and went behind it.

Following this, my eyesight was getting progressively worse, so I asked the driver, "Do you see anything?" - meaning, "Can You still see?" He obviously thought that I was asking him if he saw any Russians for he replied, "No." Well, I concluded, in that case I better go back for help, but when I informed of my intentions he said, "You look like a mess, your arms and face!" It was only then that I realized that I was indeed wounded. Both of my arms were burned - the right one so severely that the skin was rolling up. My shirt was completely burned off on the right hand side, and when I touched my face and head, all I could feel was a gooey mess. Moreover, my hair was totally burned away and blood poured over my face. Considering the extent of my injuries, it was incredible that someone had to tell me that I was wounded before I realized that I was injured! With comprehension came pain and I found that the only way I could relieve the excruciating condition of my arms was to raise them above me.

It was like this that I stumbled my way back down the hill, barely able to see the track marks our tank made in the grass, to the gravel pit where help and safety awaited. By this time, all that I could see was a milky blur in front of my eyes, and a voice called out, "who is that?" "Rudi, from Tank 541!", I replied. "Oh, my gosh," he exclaimed, "is anybody else alive?" "Yes," I answered, "the other three are hurt, but we can't get them out and they need help." "Alright," he said, "we are getting help for them!" My sight, by this time, was almost completely gone, so I called out, "I am blind!" "You just stand there, help is coming," he replied. I was told later that one of the tanks broke away from the battle formation and towed my tank and crew back to safety. I went into unconsciousness for all I remember was that someone was speaking to me while I was lying on a cot most likely on the ground. Whatever he was saying seemed to me incomprehensible. According to my Verwundetenkarte (a tag with medical and other information that accompanies the wounded soldier), I was given the Last Rites by the Chaplain. My loader's and my conditions were considered grave enough that they had given us up as beyond help and, expecting us two to die shortly, they left us in the Field Hospital rather then ship us back to Germany.

After about two weeks during which time I was still unconscious, my health began to improve and I recall gaining consciousness just as I was being unloaded from the troop train in Dresden, Germany.

egads,

a bunch of miracles in THAT tale
- 2000 m first hit
- cannon removed
- chamber entered
- round explodes
- additional rounds explode
- complete crew survives

How did it fair vs machines llike the Jagdpanther? And how badly damaged it was after receiving a Panzerfaust charge?

I think most of the Jagdpanthers were used on the western front along with most of the Jagdtigers.

Thats a pity, I would imagine that a couple of well-positioned Jagdtigers guarding a few chokepoints would've caused quite a bit of havoc in something like the Battle for Berlin.

And whta about a Hetzer? Does anyone here jnows what Hetzer means?