This one penetrated, but the soldiers life was saved by his helmet.
http://www.youtube.com/watch?v=7y0g6PNqBiI
When my brother came back from Somolia 1n 1992 after Mogadishu, I (we, whole family went actually) visited him at Ft Benning and attended a ceremony and stuff, anyway, 3rd Bat Rangers barracks had offices of some sort in one part of the buildings (forgive my memory, it was 19 years ago!) and they had a lot of trphies of sorts, captured weapons, gear, etc. Anyway, he showed me a bunch of pics they had taken in Mogadishu after the raid, one I remember quite clearly was a pic of one of the guy's "clay pots" they called them, their helmets. Anyway, seems a Somoli had fired at them and one round ricochet'd off a wall and smacked this guy right in the helmet. The pic showed the helmet, whole side of it peeled open and just obliterated, but it stopped the round. Granted, the ricochet off the wall absorbed a lot of energy and slowed the round down quite a lot, but it was still carying quite a bit of energy, def enough to kill a guy wearing a steel helmet. As it ends up, it knocked the guy out cold and he wound up with a bad concussion, but was carried out and lived through it.