Hmm, you obviously do not understand terminal ballastics very
well. Yes, the projectile will punch a hole through armour, but in
the process, the forces involved in the impact will cause the
projectile to break up after which it will enter the target along
with pieces of spalled armour to bounce around shredding crew and
splattering ribbons of gore all about, play havoc with the interior
equipment, and probably set off fuel or ammo...
Chi-Ba-Boom. The projectile will still behave like an APFSDS round,
fired from a conventional or EM gun.
The only way a projectile will overpenetrate without breaking up is
unless it was used against a soft-skinned target, in which a
projectile like a sabot dart will pass through causing little
damage. But then again, such ammo was intended for hard targets
anyway, namely MBTs.
Anyway, there's nothing to say why you can't launch HEAT or other
kinds of ammo from an EM gun as well. Basically, the higher
velocities will make targeting a snap. And since it is a direct
fire weapon anyway, don't have to worry about overpenetration,
unless u got a bad mix of friendlies and baddies around. In which
case, your AP ammor better do what it is supposed to do and break
up inside the armour rather then blasting out the other side.
Overpenetration has been documented before, in the Gulf war where
the Abrams APFSDS could blast through two T-72s and destroy them
both. Make sure you array your forces properly.
Ps. If you fire an Abrams 120mm APFSDS round on a ballastic arc, it
would actually go about 20 kilometers out!