Please, note that every stats are at 1-2m from target !!
Note also that weapons lose damage with distance, depending on weapon's category principally
So, to resume: Average lost damage in % :
A pistol: 35%
A shotgun: 60-90%
A SMG: 35%
A rifle: 5%
A sniper: 2%"
This is lost damage at quite far distance, 1500u to be exact ^^
(these average can vary on some weapon)

If you saw sometimes a 2bullets in the head with p250 to kill, it's because of distance !
Last note, What you see on your screen is not always exactly what the server take in!
"You clic, info' goes to server, which calculate it, then send back info' "
A shot in neck is sometimes in the chest according to the server