Excerpt from:
http://yarchive.net/mil/ww2_tank_armor.html"Certainly the US had the expertise and facilities to produce
cast AFV hulls and turrets. As another poster detailed, most of the
many M4s we produced had cast turrets, and a majority had cast
hulls. Castings, though, have certain inherent disadvantages. No
matter how metallurgically sophisticated a nation is, the physics
dictates that grain orientation cannot be controlled, and grain growth
is mostly uncontrollable, in large castings. Thus even the most
elegant tool steel alloys are not particularly strong as raw castings,
without work hardening to make a fine grain structure. Casting's main
advantages, once the tooling is built, are production rate and lower
(not higher!) technological requirements."
http://www.tqnyc.org/NYC073871/Comparisons_of_tanks.htmThis site pretty much shows the weight/armour difference between Pz4 and T-34(and M4 if you like). T34 is 10 tons heavier and has actually a bit worse armour in terms of resisting penetration although commonly considered superior to Pz4. Pz4 does not have as effective sloping, though, which probably would make a difference in close quarters fight. In longer ranges the sloping starts to lose its effectiveness since the hits start to have more angle but it still is the most optimal layout.
Face hardened plate has a better chance of deflecting the AP penetrator away or making it shatter on impact where as the softer cast armour lets the penetrator bite into the surface and start delivering its energy to armour. Rounding of the corners is certainly a good feature (although softness of metal eats some of that away)as are the lack of welds in the corners in cast armour and of course it is fast and cheap to produce.
Some more info:
http://www.achtungpanzer.com/pz3.htm#panzer4 I tend to agree that M4 was still just an M4 although now it had a decent gun and it could defend itself also in head-on engagements.
It is up to you to consider if M4's armour (and T-34's) are a bit "overdone"...
-C+
