The soldier in the probability section updates in the wrong direction. If you survived two shots to your helmet, then you were almost certainly not being shot at with a sniper rifle. For instance, my Mosin Nagant (a bolt-action 7.62x54mmR) will penetrate both sides of a WWII era infantry helmet (and presumably, a "soft target" in between) every single time (although, at a shorter range).

BTW, love the article.