[c_of_red]

IIRC, the rounds were different also. The Germans used a ballistic capped shell, while the US and Soviets were straight AP. The Ballistic cap allowed the shell to 'stick' at greater angles. Plus the Germans used face hardened armor while the US and Soviets used rolled homologous armore, which had the same hardness all the way thru (hopefully, if the mill was having a good day). Face hardened armor tends to cause more deflections at an acute angle and can break up non-capped shells. On the down side face hardened armor tends to spall more and suffers greater damage from overbore hits. A guy namd Lorin Bird wrote a book analysing the gun vs armor thingie in WW2. The 2 big discoveries he made was the existance of what he called the "shatter gap", which is a energy range were the shell breaks up instead of penetrating the armor. A little slower or faster (which equals distance downrange) and the shell penetrates. The second was with oversized hits, where the shell diameter is greater then the armor thickness. IIRC, the energy levels can be great enough to shear off a section of armor and continues on the original trajectory of the projectile. That is one reason why the soviets lost so many T-34's. The shell would glance off the sloped armor, but in the process it would send a chunk of that armor into the T-34.
The Soviet steel wasn't as good as everyone else's. Poor quality control and the need for volumn. The USA didn't face harden it's steel for the same reason. Volumn was judged more important then a little extra protection.