“Many, many soldiers tell of shooting an enemy combatant and watching them run off as the bullet zips right through them causing only a tiny hole and little damage.”
They missed.
Nope. The enemy would fall or flinch when the round hit him but still continue fighting. The round went through him and caused a wound like an ice pick, small and straight through. Many times an enemy combatant has been killed or caught with old, healed 5.56 bullet wounds in them.