Any round from .375 H&H on up would zip right through the toughest body armor made right now. I'm sure something could be made that would stop a big bore, but the weight would be so much that it would impractical to wear. Plus, there's not a whole lot of taliban muzzies shooting 416 Rigbys.
Body armor is made for small arms and frag, it's not capable of stopping big bore hunting rounds.
