Lethality can come from bullet design as well.
I’ve noticed my Kurd friends in Syria have been begging the US for heavy weapons. The snipers they have are increasingly using much heavier rounds and bigger bore weapons.
One of my Syrian friends tells me that she has never seen Kurds waste ammo or shoot in the air. Guess that is something they learned in Kobani. They were very close to running out of ammo at the point where we brought in the first air support. They made every bullet count.
I also believe the Kurds in the North hunted more than other "tribes" and this may have something to do with it.