Er, sorry for the double-post but, I'm going to learn you guys some stuff about tanks.
The Sherman III with its 75mm gun could not penetrate the Tiger's frontal armor at any distance, even point-blank. The Sherman would have to use their superior numbers, speed, and performance to maneuver around to the sides or rear of the tiger and shoot it from relatively close ranges, some 150 yards or less.
This all changed with the introduction of the 76.2mm high-velocity gun on Sherman IVs and Vs. They now had capable armament and thicker armor (75mm increased to 100mm) where the Sherman was likely to take a hit. The new armament allowed for the Shermans to be able to knock a Tiger out from as far as 700 yards. This was still a lesser distance for a Tiger to knock a Sherman out (roughly 1200 yards), but it was a great improvement over the crappy 75mm cannon.
The British had their own solution. They mounted a powerful anti-tank gun, known as the "17-pounder," into a slightly modified Sherman turret, took out the hull MG to make more room for ammunition, and tacked on more armor as well as making the ammunition somewhat explosion-proof if hit by an enemy shell by surrounding the ammunition crates with water tanks. The Firefly's 17pdr gun was extremely remarkable, and it was on equal terms with the Tiger I's 88mm L/56 gun. Now, with the King Tiger's 88mm L/71 gun, this was a whole different story. A conventional tungsten AP round couldn't penetrate nearly as well as the King Tiger's could, but when the 17pdr was loaded with Armor-Piercing Discarding Sabot (APDS) rounds, its gun could penetrate 1.5" more armor than the King Tiger's could! Holy crap!
As for the Pershing, it was far superior to the Tiger I, being better armed and armored, but inferior to the King Tiger. Its 90mm M3 gun was powerful, yes, but it couldn't punch through armor nearly as easily or as well as the King Tiger's gun could.
Now, moving on to the IS-2. The IS-2 didn't have the armor piercing capability of the King Tiger, but its 122mm main gun's HE (High Explosive) rounds, on many occasions, blew the King Tiger's turret right off. Either that, or the shockwave from the blast was so intense it knocked out or killed the King Tiger's crew. The only drawback to the IS-2's gun was that its shells were two-pieced (the shell and the gunpowder, loaded separately) and extremely heavy, as opposed to the King Tiger's one-piece ammo weighing some 28 pounds or so. Also, the King Tiger's AP round could very easily punch right through the IS-2's frontal armor, so in a non-mobile battle they were just about on par with each other.
Now, how about that little gem, the T-34? I've read stuff on this thread about 76mm guns and 85mm guns. The first T-34s had a 76mm main gun. It was soon upgraded to a more powerful, longer 76mm gun. While the longer gun (An L/42 I believe - the length of the gun is 42 times the caliber) was very good for its size, it didn't compare in the least to the newer, longer 75mm guns being mounted on the German Panzers leading up to the battle of Kursk, not to mention the Tiger's deadly 88mm. After Kursk, this fact struck the Russian commanders like a brick. The T-34 was no longer superior. It needed a larger armament. So, a modified 85mm anti-aircraft gun was fit in a new, better armored turret, and so the T-34 was superior once again. Its 85mm gun could penetrate the Tiger I's frontal armor at 400 yards, while the old 76mm couldn't even penetrate the Tiger's side armor at 100 yards. Now, 400 yards isn't much, even compared to the American 76.2mm, but with the ever-increasing numbers of the T-34/85 variant and its superior offroad performance and speed, the columns of T-34s were able to quickly close the gap between themselves and the enemy tanks shooting at them from ranges of up to 2 kilometers and destroy them.
Reason: Question answered, continued posting is un-nessecary :banana: