When a blacked out limb is it, the damage is multiplied by 1.79 then distributed among all remaining limbs. Zeroing out the chest kills the target, either by secondary damage from another limb or direct hits. Zeroing out the head kills the target only if the head was hit, bleeding the head to 0 from secondary damage does not kill the target. It takes 5 shots to kill a target with 7.62x39 PS ammo when aiming for a leg. It takes 2 shots to the chest to kill a target (wearing no armor or paca) From this we can conclude that center of mass or head shots remain the fastest way to kill a target if the ammo is capable of penetrating the armor. If the ammo can not penetrate the armor, then aiming for limbs is the faster way to kill.