ORIGINAL: Curtis Lemay
The M4/76 in the game is probably a Korean War version. (Remember Norm's Korea scenario). For use in WWII it should have a reduced AT value. I believe there was a problem with the shells being too hard, making them brittle, that wasn't fixed till very late in the war.
M10 TD in TOAW also has the AT value at 16, I don't think M10 Wolverine served in Korea. And I think AT=16 come from M1gun's APCR/HVAP ammo M93, at 500yards, M93 can penetrate 157mm armor at 30 degree.
I agree M4/76 and M10's AT value should be reduced for WWII scenario, otherwise it makes TOAW tank battle weird. I remember this is a TOAW's mechanism, when AT value >= Armor value(no matter what the armor value number is), the possiblity of penetration = 100% (equal to destroyed in TOAW), if AT value<armor value, then the possiblity of penetration range from 0%~99%, a formula is going to be decided what the chance is (I can't remember where I can find the formula in the handbook, appreciate if somebody can help me)
so it means M4/76 and M10 TD can kill Tiger (Armor=10) or Panther(Armor=13) with 100% possiblity, it can even kill Kingtiger (18) at very high possiblity. In reality, M1 76mm gun performe poorly in front of Tiger and Panther, regular AP ammo M79, which is 109mm/500yard/30degree, shattered on Tiger's surface harden armor. it also has fair chance to penetrate Panther's front turrent and low hull, but it has almost 0% chance to defeat panther's upper hull.
the other explanation here is this AT=16 value is for M93 APCR/HVAP, but it is weird too. in real world, M93 is very rare, most of the tank can only get 3-4rounds. Also In TOAW if M4/76 can have this high APCR AT value, why other WWII tanks have their regular AP/APC value? why M4/76 and M10 are so special?
And yes, M93 is like most of other WWII era APCR/HVAP, it is very brittle (because of the technology to treat and form Tungsten/Tungsten-carbide during that time), it has very high chance to shatter on the sloped armor. if my memory serves me well, I don't think american did anything to improve the M93,instead they gave up the R&D on APCR and focused on HEAT after war. But they did some improvemet on regular AP M79, they add Ballistic Cap and make APCBC. this part is just my memory, might be wrong.