What I've seen
I haven't tried any steel plates, but what I can say is that the Speer & Hornady 350 grain hollow points will penetrate:
A car, front to back going through the windshied with zero deflection, seat, seat back (front), seat & seat back(rear), a trunk hinge part, metal surrounding the rear tail light assembly, rear tail light assembly and several inches of earth.
It won't penetrate an engine block, but it will crack the water jacket quite severely after penetrating the grill, AC condenser, & radiator.
YMMV of course, but those were my findings...witnessed by 15 other people.
HTH