When a target is in single fire range. the AI will shoot at him with the exact same interval between shots continuously. Its always 0.7 seconds between each shot Like a robot is controlling the gun.
normally when you fire is controlled by when you get the Enemy in your sights. Since AI aiming is controlled by the computer. This takes the same exact amount of time each shot.
when a human fires he may fire one shot, then wait a second until he gets the target again. Then fire 2 shots in quick succession, Anyways the time between shots is always different.
BIS should add a random variation for time between shots, or maybe try to create a pattern that seems like a real human trying to aim and fire and reaim.