Locations are partially dependant on your setting. For example, if its shooting and both sides have good body armor, then center of mass shots may do nothing. Also, with/without armor, as magic8ball said, actual hits to a head tend to be more severe.
A flesh wound, for example, imposes no penalties to the head you state. However, consider the flesh on the head... eyes, nose, throat, ears, forehead. A flesh wound to the eye is quite a bit more severe than a flesh wound to the chest. A flesh wound to the forehead, besides causing bleeding into the eyes, can daze you as your brain gets rattled.
Also, trauma to the head has a much greater chance to cause a loss of consciousness.
|