I don't have any experience shooting people with a 5.56, but from my experience shooting deer with one the only way you'll drop one is with a headshot. Shot one in the head and it curved around her skull and came out her throat. She was dead before she hit the ground and didn't hardly have any blood left in her. Got a body shot one, and while it took out his vitals, the entrance wound was so small we couldn't find a blood trail and just lucked into finding him.