Shoot Around Cover. Not Over It.
Cover will stop or deflect rounds. Usually, cover incorporates concealment but its most important feature is its capacity for protecting you from hostile fire. The primary reason to seek cover is to avoid being shot. Your ability to effectively return fire from behind cover safely is a secondary consideration. Cover is by no means impenetrable and is dependent upon what weapons system is being employed against you. Many bullets will blast right through a block wall no matter how big it might be. Do not think of cover as something to get behind but something to put between you and the bad guy.
Whatever form your cover takes, here are some general considerations to remember:
Unless you want your head to look like a canoe you will be much less exposed firing around your cover rather than over it.
The exact posture you adopt will depend on the shape of your cover and the suspect’s location.
The idea is to get on target while risking as little of your hide as you can.
When you’re forced to stay behind cover for a long period of time, gradually develop your position so that it does not restrict circulation, add to your fatigue, and prevent accurate shooting.
Your position should be a position of advantage, as comfortable as possible, and functional so that you can advance or retreat from it if necessary.
Think outside the box and find genuine cover and keep it between you and your adversary as cover is a lifesaver.