It seems like you just pray and spray with the damn thing. I went back to SA and noticed the Hunter (Apache) at least locks onto a target when you fire the machinegun. So I figured I might be missing something withe the annihilator
It sucks ass...not only is aiming difficult (would help if you could stabilize the thing while tilting), the guns are incredibly weak (you can unload into a stationary cop car for 2 full cycles, and it still won't blow) and unstable as hell.
At least it looks cool and can withstand a ton of punishment.
That specific camera will always line up to where shots should be slightly above and left and right of the center of the screen. It should be easy to see where the bullets are going after a few minutes of playing with aiming in this manner.