Snap shooting is something I learned a few years ago that can make one well trained, aggressive shooter, able to defeat many lesser-trained opponents. The idea of snap shooting is to present as small a target as possible while quickly peeking out and delivering accurate fire, and then returning to your cover.
In the movies you always see the bad guy will put his back against a corner, using it for cover. He then turns the corner, exposing his entire body, raises his weapon to take aim, and is promptly shot dead by the good guy. Snap shooting aims to correct all the mistakes of this very poor example of how to exchange gunfire with someone who aims to shoot you.
When someone is shooting at you, you obviously want to expose as little of yourself as possible, for as short a duration as possible, to minimize the chance of being hit. At the same time, you have to deliver accurate fire when you do expose yourself to make the risk worth something.
The first thing to know about snap shooting is how to properly use cover. Ideally you will have some decent cover to use (something that can stop incoming rounds and provide concealment) In our movie example, the bad guy puts his back up against the corner and then turns the corner and exposes his entire body to make his shot. In doing this, he has limited his visibility of what is going on, by facing away from the target, and as he presents himself, does so in a way that maximizes the enemy’s likelihood of hitting him. At the same time, because his weapon is not raised, he must expose himself for a longer period of time to aim his weapon and fire.
Stand, or crouch behind your cover, facing towards the enemy. You want to put yourself far enough off your cover so that you can pre-aim your weapon, and also be mobile enough to quickly move to other pieces of cover, or move to flank and continue engaging your target. Raise your weapon and get proper sight alignment towards where you believe your enemy to be. This will save you the time of doing later outside of cover.
Now that you have your weapon raised and ready to fire, quickly peek out with only your barrel and eyes, putting your weight on your right foot (left foot if peeking from the left side of cover) and bending at the torso. Only expose what is absolutely necessary to get an accurate shot off. Fire as many shots as you feel you can safely and accurately, and then return to your previous position behind cover. (This should just mean bending back to cover from the torso.)
In the space of a second you can peek out, exposing only your barrel and eyes, shoot off a couple of well placed shots, and bend back into cover. This technique should be used to fight your way into a position of better cover, more advantageous shooting positions, or for flanking your enemy if working within a team. That is not to say that this is only good for aggressive movement, but is also fantastic for defending a fixed position or close quarter battle. With practice you can become very fast and remain deadly accurate, while only exposing a very small target for your enemy.
Being “backed off” from your cover so that you can peek around also allows you to have greater situational awareness. Greater situation awareness can win the battle, and often does. Also be sure to peek out from different positions so that you do not become predictable. You can peek out standing, crouching, on the left or right side. Just keep things mixed up to throw off your enemy. Here is a good example of some snap shooting being done by a paintball player. [JWR Adds: I consider paintball a useful adjunct to tactical firearms training. Just beware that paintball competitors have a tendency to start subconsciously thinking of concealment as cover (since paint balls have minimal penetration), and they also develop a “60 yard mindset” wherein they feel safe to maneuver if they are more than 60 yards from their opponent(s). Modern centerfire rifles of course have 400+ yard effective range!]
One might say this is something paintballers use and doubt its effectiveness, but its effectiveness in paintball translates into the real world as well. So practice snap shooting the next time you go out to shoot and see just how fast you can engage targets with accurate fire from cover. One very skilled snap shooter can defend very well against many untrained shooters. I spoke with a friend of mine who is an Army Ranger and got through most of Green Beret training before suffering an injury that put him out of training. He never trained in this style of shooting! It is somewhat surprising that something people who play paintball use all the time and is extremely effective is unknown to nearly all combat forces. Make sure you have the edge and train to snap shoot!
I recommend the AR-15 with a 16″ barrel for this, or another short rifle, because the AR-15 rifle is lightweight, light recoiling, and accurate. It lends itself well to snap shooting. The .223 is not and will never be a .308, but will allow you to carry more ammunition for suppressive fire when working in a team of two or more, so you can cover one another and out flank your enemy for killing shots if you cant score them from your current piece of cover. Good luck and train hard.