In Dead Trigger, head shots seem rather sporadic, which can be frustrating, especially when dealing with these guys:
Four or five point blank shotgun rounds into the face, and the only thing I get is the ping-ing noise of his stupid helmet protecting his stupid face. Reminiscent of Goldeneye: 64, where the guards had helmets that could stop a .44 Magnum.
The issue isn't just limited to the armored undead gentlemen, however: all the zombies seem to have some magic ability to frequently shrug off head shots. It's extremely obvious when using the "Big Head" powerup (I can't remember exactly what it's called right now, something like "Head-flator"): there's really no question about whether or not I'm actually hitting their head, but frequently it takes two or three shots to actually register a head shot.
What exactly determines whether a hit is a head shot or not? Is there a chance factor? E.G., if you hit a zombie in the head, the game rolls a d20 behind the scenes to see if it actually was a head shot or not?