Also its tactics. The US went in with the belief, and I'm serious, that tanks would not fight other tanks. The sherman didn't NEED to have a good gun, or good armour, because it was never actually meant to fight against other tanks, that was the job of the tank destroyers, which were supposed to be light, fast ambush tanks with slightly better guns. Of course, this entire tactical dogma was bullshit, but generals like Patton harped on it continuously, and thus thousands and thousands of american tankers died trying to fight german tanks. When it was finally realized that something was wrong, it was impossible to fit good guns into the Sherman tank, which is where you hit upon Josh's post. The british had to turn the 17lber sideways just to fit it in, along with a modified turret. The Germans couldn't fit anything larger then the long 50mm into the Panzer 3 for same reasons, the turret ring couldn't accommodate the size turret needed. As for armour, simply saying "ah, we'll make it thicker" isn't a fast solution. Entire factories would have to change over, entire specifications would have to be rewritten, the added weight would have to be dealt with with new enginers, new powerplants, new track lay outs, new crew layouts, etc, etc, etc. All in all, it was simply more economical to continue to produce a piece of crap. Remember, the Tiger had been in research and development since before WW2, but it took until 1943 to take to the field.
