I've personally shot a Barret 50 cal that easily penetrated 1/2" of plate steel with incindiary (sp?) rounds. Not only are they designed to pierce tank armor, they are designed to shoot through engine blocks and through reinforced concrete walls of up to 1 foot thick. Kinda scary stuff. Ironically, the same guy who owns it has an ex state department Excursion, fully armored with night vision, an air filtration system that filters out bilogical and radioactive agents, run flat tires with kevlar center donuts, and a bunch of other ridiculous stuff. It runs a supercharged V10 and was designed and used for leading processions and being able to drive through a bus if needed (ie the road was suddenly blocked). Pretty wild stuff.