To be a successful shooter, you must have a few things going for you: a good sight picture, a smooth trigger pull and follow-through as the shot is fired. With the general-purpose rifle, or AR as some call it, there are a few other things that can help increase your effectiveness at tactical shooting
Today, I still often see people placing their support hand on the front of the magazine well in tactical shooting. This isn't a huge problem — unless you're worried about accuracy, speed and retention of the carbine. As a tactical shooting instructor, I would stack these three as prerequisites for employment of this system.
Many people engaged in tactical shooting feel that reaching farther out on the carbine's handguard is a nontactical technique. They feel that a more compressed body position is better when pulling the trigger. I could not disagree more with this statement.
As a tactical shooter and a tactical shooting trainer, I motivate our students to be as accurate as possible while pushing their speed to the ragged edge. With the hand holding the front of the magazine well, you're giving up the leverage you need to move the muzzle quickly from target to target as well as hold it steady when you arrive at the aforementioned target in tactical shooting.
Couple this with the fact that you will more than likely be operating at night, so a light or laser will also be used while tactical shooting. If you look at your carbine, attaching the pressure pad or light mount to the forearm just makes practical sense. Let's go a step further.
In carbine competition shooting, the best of the best in tactical shooting will shoot with the support hand pushed significantly out on the forend of the rifle. I believe that the use of this grip in competition is part of the reason tactical shooters have been slow to adopt the technique as well.
Many of those in tactical shooting feel threatened by civilian competition shooters and their abilities, so it makes sense to simply say, "That is a competition thing; I am a tactical shooter." This is a cop-out. If competition shooters can shoot faster than tactical shooters in a tactical shooting situation with increased accuracy, why wouldn't we adopt their technique as quickly as possible?
Only you can answer that question. I am a tactical shooter who loves competition, so I want every possible advantage I can obtain from the tactical shooting and competition arenas as long as it fits sensibly into my world.
Extended free-floated rail systems have allowed us to easily move our support hand as far out as we deem necessary to drive the rifle quickly in tactical shooting. I also use a short vertical grip to allow the rifle to be pulled stiffly back into my shoulder, which helps with recoil management as well. You cannot totally eliminate recoil with the AR, but you can adapt to it quickly.
As with the pistol, I try to keep my shooting hand somewhat more relaxed than my support hand. Since the strong hand is manipulating the trigger, I need finer control and less tension to help with this process. At the same time, I do try to get a high grip on the pistol grip to help with control. Any space left between your firing hand and the bottom of the lower receiver will work against you when shooting quickly.
Shortening your buttstock is not the answer for allowing the support arm to reach forward. A collapsed buttstock takes away the needed power from your shooting and fighting stance. Some schools teach a completely different stance for tactical shooting than we would generally fight from.
I am of the belief that a fight is a fight, so get into a good fighting stance. This may mean using a rifle or pistol, or, if you live in a state that does not allow law-abiding citizens to own guns, you better get good with your fists. All of these stances should be very similar.
If you are planning to fight with your fists, put them up in a position where you feel most powerful. Now adjust your buttstock so your fists can stay in the same position with the carbine. An easy way to quickly determine the correct length of pull is to place the buttstock in the crook of your shooting elbow and grab the pistol grip. If your wrist has to be bent or distorted to grab the pistol grip, your stock is too short.
Back to the task at hand. What is the correct distance to slide your hand forward on the forend of the carbine? This is a question that only you can answer. I like to reach out pretty far, but then again, I have long arms. When I reach, I do not twist my elbow up and over so that I become contorted, as this adds stress to the support arm and does not allow for speed when driving the gun. It is also slower to conduct manipulations with a contorted arm and elbow. I do clamp the forend with my support-hand thumb riding down the side of the rail, and sometimes I place it over the top of the rail if the circumference of the tube is small enough.
Ideally, you must also be able to access your light and laser switches if you are operating in the tactical shooting world, so be aware of how you will make this happen. I have tried many different setups, and I always seem to come back to an upper-left or lower-right mount.
If I have a 12 o'clock laser in place, I use the white light mounted on the lower right, which allows the thumb to reach past the vertical grip and activate the push button on the rear of the light. When shooting with the support hand, I can still reach the light by loosening my grip and reaching forward with my thumb. If I'm not using a laser, I can use the same light positioning or place the light on the top left edge of the rail, allowing the right and left thumbs to reach the light's tailcap if things get dark and scary.
The last technique is the positioning of the shooting-side elbow. In the past, we would see a lot of shooters with the shooting elbow held relatively high, and this continues to transcend from rifles to ARs even though it is not necessary for a great tactical shooting position.
Lowering the shooting elbow will help you maintain cover as well as allow for smooth movement in and around obstacles. If you need to throw an atomic elbow during a close-quarters confrontation, having the elbow already low will allow you to step into it and throw a very vicious blow.
Head out to the range, and see what works for you. Try sliding your support hand forward, and practice pushing the carbine quickly from one target to the next. You will soon see how much quicker you move and better you will be able to control your carbine once you arrive on the next target in a tactical shooting situation.