I've seen a handful of head shots, and none of them looked like what you describe. Actually, all of them had a nice, neat hole, and a lot of blood.

Apparently youve never seen a 5.56mm round impact in the small corner of the eye. It literally splits the head open at that point the top of the skull fans out like a banana peel.
Or six 5.56mm rounds impacting starting in the chest and zipping up into the jaw and through the center of the Tbox...., where all thats left is a lower jawbone and chunks of skull held together by flesh that fan upwards like a torn doritos bag, where part of one eye socket is hanging to the left side and theres nothing but pink matter on the right.
What exactly head shots have you seen? Because ive seen about 8-10 pictures of real kills done with rifles and M249s and none of them looked anything like a neat hole....