Kevlar helmet bullet stopping ability

Here is a video of a Marine shot in the head, the helmet takes a punch but holds … show-clips. Any way to tell what hit him? Somehow I feel from the head swing that it is something small like a pistol round. So how wrong am I?

You cannot be sure but the foot pounds of energy remaining in a presumed sniper bullet would knock the head back like he had been hit with a baseball bat. I would have thought, unless it was a glancing blow.

There was a guy a few years back doing destructive field testing of British police and military vests and helmets but I cant find his website now. That may be significant, the results were “controversial” particularly if you were being sent out wearing them