I've seemed to have a problem the last couple sessions we've had with player's using terms like "I shoot him in the head".. And then after the attack is rolled saying things like, "well since I shot him in the head he should take extra hits or add a negative die next roll." Or they'll also say things like "well this is my third time I've shot him in the head so he should be having convulsions or almost dead." (Keep in mind they were fighting a hutt). If I say no, they'll say things like "well you have to be logical. If I shot you in the head three times, you'd be dead."
These guys are friends and family so I don't want to be rude, but at the same time, I don't want them to make themselves overpowered or exploit the system, since there is nothing mentioned in the rulebook about stating where you are firing on the opponent.
Any advice from you player's or GM's? What would you do in this situation?