I was trying to pass the 10th level of the Sharpshooter challenge, which is to disarm 6 opponents without changing weapons or reloading. This could be a bit tricky, except I noticed when I was using the deadeye mode and taking a shot, it didn't lower my ammo count. I could (and did) take about 10 shots from my 6 shot revolver, one deadeye run at a time, and I still had all my bullets. Made the challenge pretty easy, once I realized it. I assume this is a bug...has anyone else encountered this?
Dead-Eye mode automatically reloads your weapon for you. Since you are not manually doing it, it doesn't count as an actual reload. It might be why your ammunition count didn't change.