The Head shot bothered me. When they first got to the guy who was shot they were looking for the wound. A .223 to the head would take off a good chunk of skull and would be obvious.
A solid hit with a .223 at close range will turn your average hominid skull into a canoe.
You are correct. We saw what the AR did to an arm at close range. The wounds are not consistent. And from the video, the first shoot would have been at close range.