If you are running an AR platform or any weapon system with its sights higher than the bore line, a common problem that is seen is the striking of cover instead of the bad guy. The sights may be clear of the obstacle, but the muzzle may not be. This problem can become less obvious the further you are away from your cover. You need to make a quick visual check that your muzzle is clear then shift your focus to your sights.
This sight/bore offset can also make a difference during close range engagements. At distances of 25 yards or closer you may have to hold your point of aim as much as 2.5 + inches high to place your round where you want it.