Corrected entry: In the beginning of the movie, when Charlie is setting up to shoot, he pulls the slide back on his rifle and the bullets are shown. They are in the rifle backwards.
Correction: You are completely wrong. The scene at 24:14 depicts the action in standard view and there is no way the bullet points should be facing against the action of the feed.
Corrected entry: At the end of the movie when Jack drives the Mercedes in reverse you can hear him going trough the gears. There's only one reverse gear. There are no more gears.
Correction: Indeed it only has one reverse gear, but what you're hearing is Jack getting on and off the throttle as he maneuvers the car backwards through the quarry. If he had just gone full speed he would have likely spun out or hit an obstacle prematurely.
Corrected entry: If the shooter was parallel to the victims, on the bridge, then the police would have known where the shots had come from. Especially the water-bottle shot. If the shots had come from a 90-degree angle (as compared to shots from the parking garage) they would have definitely known it.
Correction: The ammunition is not in backwards, the camera angle changes to a reverse direction. When Charlie starts to pull the slide back, the tips of the ammo would be facing to the viewer's right (Charlie's left). Thus, during the close up, the viewer expects the camera just "zoomed in" and the tips should still be pointing to the viewer's right. But the camera switches to an overhead shot from Charlie's prospective and the tips are pointing to the viewer's left, which is still Charlie's left.
Bishop73