I'm agreeing with Zedul here. This used to drive me crazy when players asked for this. But combat is just like Zedul was saying. It's not just "swing! swing! swing!". I assume that a lot is going on in that 10 second round: some footwork, feinting, adjusting your grip, ducking, etc. To me, a character's OB reflects their
skill at fighting with that weapon, which boils down to a lot more than how hard you can swing it. Ultimately, any successful attack and criticals achieved is the culmination of this action and skill, when an opportunity to strike finally presents itself and the attacker has the wherewithall to seize it! And if no lethal attack was possible, a skilled fighter will weaken his opponent with the most effective strike available.
So, in comes the called shot. Usually goes something like this: "I want to hit him in the head!" (personally, I've never heard anybody call anything but the head), the common belief usually being that it should be harder to achieve but more damage delivered if successful... or something.
So here's what I hear when players use a called shot: "I don't want any criticals that aren't on the head!" So that critical that sent that guy's hand flying off? Sorry, not the head, didn't happen, no damage, no crit
This explanation usually cures this whole called shot nonsense