Segue algumas importantes informações:
The IS serie, along with the KV and all the assault guns derived from them, formed a massive contributiuon to the Red Army. As all the Soviet tanks, they were built rawly manufactured wiith the mind pointed to the essential, but what they lacked in sophisticated weponry was more than balnced by the power of the large calibers. They had to pay for the limited ammunition load, but the IS tanks represented an reliability and mobility model their opponents could not match. As conseguence they were able to give a well protected heavy fire power which played a vital role in the Soviet offensives leading to the fall of Berlin.
Stalin tanks and the German heavies
While the anti-tank role was not as primary as the infantry support role the IS tanks had to front the German Panthers, Tigers and Royal Tigers.
Their 122m gun was a good anti-tank weapon but it still lacked of the armor piercing punch . Several projects were carried to re-equip the tank with a more performing gun: discarding the 85mm gun (also in tis improved versions) the only real alternative was the 100mm D-10 gun.
Still the industrial facilitation in having a great reserve of 122mm tubes and ammunitions and the 100mm's lack of support took the previous gun to be retained.
Survivability is a fundamental. It is usually forgot that a tank (and its crew!) nevertheless being heavily armored and gunned, may always being hit, immobilized under enemy fire, etc. It could take fire or not (and IS-II greatly reduced this thanks to his Diesel engine), ammunition could ignite and blast it but wheter or not these things happen a reasonable chance for the crew to escape dangers must be given.
German tanks had two hatches in the turret (commander, gunner and loader) and two in the hull (for driver and marconist). IS II only had two, both located in the turret making the driver's chance to escape, to say at least, difficult (although there was no turret basket to divide the turret from the driving compartment).
The Panther and IS-2 guns had a roughly equal armor piercing capability on ranges of 1,000 metres while the Soviet 25Kg HE shell performed much better than German 4.7Kg one. Stalin enjoied a superior all-around protection while having about the same weight.
The 122mm shell was able to pierce Panther's front plate on a range of over 1,000 metres while, according to Panther's crew manuals, the German had to get close to 600 metres to score a sure hit over the Russian. Both tanks could pierce each other flanks from range up to 2,000 metres.
The Panther's advantage in speed (46 Kmh versus 37 Kmh) should be considered in formation and manouvered combat.
The confrontation between the Tiger I and the Stalin also take an advantage to the Stalin. It have better armour, lesser dimensions, lesser weight, bigger gun. But this have a price: Stalin was much more cramped and could take less then one third of the ammunition carried by a Tiger and the German tanks had a much faster rate of fire.
On a 1,000 metres range they could knock out each other but going to a range of 1,500 the IS-II could take out the Tiger while remaning untouched. However these are theoritical values: Soviet poor optics devices make them difficult to obtain and much of the engagement's results depend upon the individual crews' experience and skill.
The comparison with the Tiger II is more difficult: the German tank was much more heavily armored, had long barreled 8.8 cm gun capable to knock out an IS-II well over the 2,000 metres, a distance making it invulnerable to return fire. Luckely for the Russians the European ground in which the Tigers operated was not optimal for them, with the most of the engagements taking place at ranges of 500 metres.
Between the two tanks there were only minor skirmishes in Hungary when the s.Pz.Abt. 503 entered in action. A major encounter took place in Germany on January 12th 1945 during the Soviet offensive towards the Oder river. Tiger IIs of the s.Pz.Abt. 524 exchanged fire at short ranges with the Russians resulting in both sides catching heavy losses.
Tiger II had a faster rate of fire, superior armor and fire power and only Soviet advantage was a lightly better speed and a superior all-around mobility (expecially while speaking on the logistical plane).
http://www.geocities.com/Pentagon/Quart ... _serie.htm
No site
http://www.fprado.com/armorsite/tiger1.htm tem vários quadros comparativos de Tigers I contra Cromwells, Churchills, Shermans, T-34/85s e Stalin.
Tbm há outra tabela interessante de disponibilidade entre os tanques alemães.