Not at the gun store, but at a bbq a cousin-in-law who was in the marines for a short time informed me that if a 50bmg round got even within a couple feet of your head, it would blow your head clean off.
Didn't the 223 Remington (5.56mm) just blow off Viet Cong arms if it hit one? Believe it or not, I was told this by a guy I once worked with (he was an administrative sort in he Army, no combat).
