Body armor not so good with high cal rifle.
Also, define "body armor."
A vest? Yes, crap against most any rifle. A vest with SAPPI plates?
I've seen a plate take a burst (5 or 6 rounds) of 7.62x54 steel core rounds and not penetrate. I knew the Marine that was wearing it and lived to tell the story. I helped pry the bullets from the plate to give to him.
Unfortunately, one round "missed" the plate and hit flesh - but luckily the plate stopped what would've ordinarily killed him.
-- I know another that took two rounds 7.62x39 to a plate; aside from a bruise, he was fine.