yeah, I dont' even think about HSs, I just aim for mid-chest and below chin area.... The PP-19 puts out enough bullets, that sometimes I get lucky and get a HS, otherwise, my goal is to put effective fire on the bad guy, so that he can not easily return fire, because of the hit-box effect.
Now, if I am using my fav AR (M416 w/scope) I go for dead on chest shots.... highly effective on an enemy that is running torwards you... people for some reason don't get this... they run into the adjacent room on DeathRoom map, and I lay them out... so I get high KDR because of this.... so come call me a camper, and I'm fine with that.... in the real world, the best Camper wins.
Sniper Rifle... L96 - I hit you in the chest, your dead.... simple but effective