I have shot 7.62 AP, not the mild cored stuff that people claim is AP.
it will NOT go all the way through an iron block.
3/4" of IRON, not steel, will stop essentially every .30 round you throw at it, though an ap core can squeeze through.
AP is designed to pierce armor, not iron. Armor is made a different way. Which is why the same round that punches through 1" of armor titanium, cannot pierce 3/4" or iron. I can show you a picture of what AP does to an iron plate. just not right now.
YES, an engine will be seized after that shot, it would definitely penetrate the intial side of impact.
NO the bullet will not just "zip right through like butter". That is a figment of hollywood imagination. Tree branches deflect bullets, what do you think an engine would do?