Why? It takes 2 shots to kill some one with full health and no armor. So that means in 4 shots you can Kill some one with full health and armour.
I will say this though. I have seen a place on Samp that has headshot is an instant kill.
So that could be added.
With no armour, it takes 3 shots to kill him.
With armour and health, it takes 5.