In the bonus round, you keep shooting until you hit a square that has a skull on it. In theory, if you keep hitting a blank square, you do have unlimited ammo.
As for whether or not it's skill or luck... I think it's predetermined. I've noticed several times when I click the button, it ends up landing on almost a full square away from where it was when I clicked it. I know it jumps around but, hey, I'm just saying.
The game itself is lower variance than, say, SuperSuits. And the incrementally-calculated wilds (4x, 8x, 12x, 24x) totally kicks arse.
I got four wilds on the backend (reels 2 thru 5) in the intro tourney earlier today (16 minutes before it ended
) for a T$988 win from a T$6 bet. Those wilds can be pretty powerful...