Caution! Rhetoric follows-

What is a "Double Tap"?
Is it two shots fired as fast as you can?
Are they fired at the speed of your mouse's "Double Click"?
How do you see your sights?
Are you tracking your sights with each shot, or are your eyes closed on the second one (or, god forbid, both)?
What is your focus, sights or threat (or, god forbid, neither)?
What is the acceptable accuracy level of the shots?
At what range are they applicable for rifles? Pistols?

Rhetoric off.

After hearing the words "Double Tap" so many times I have grown annoyed in their usage, especially considering today's training market. There are much more descriptive and relevant names for methods of shot delivery, or at least ones that have some sort of institutional standard.

The above questions probably resulted in many different answers from those reading them (except for those that already know where I am going with this). About the only thing that everyone can agree on is the number of shots fired. (That would be 2, as evidenced by the word "double".)

So we are talking about 2-shot engagements, or at least the method of delivering 2 shots. The problem comes in when understanding that there are different ways to deliver the shots depending on range, skill, circumstance, weapon, and sighting systems. There are essentially three types of pairs- Hammer Pairs, Controlled Pairs, and Dedicated Pairs. Let's define each type, assuming a target size of 6" (as this is my accuracy standard for combat prep training) must be hit consistently with both shots to be considered effective.

The Hammer Pair. This is what is generally thought of by people when the term "Double Tap" is thrown into a discussion. It is generally defined as one sight picture and two shots, followed by a second sight picture during follow-though. The shots are taken as rapidly as the shooter can press the trigger, generally around 0.20 sec split times. Grip and stance are critical to achieve acceptable accuracy with the second shot at speed. It is generally applicable with a rifle/carbine at 15 yards and under, and with a pistol at 5 yards and under (more on this later). Sight picture for Hammer Pairs will generally be a soft-focus flash sight picture due to proximity (see what you need to see).
As I understand it was developed around the 1911/.45 ACP to allow shooters to quickly deliver two shots from a Weaver stance/grip.

The Controlled Pair. This is the most frequently encountered standardized method of pair delivery within institutionalized programs. It is generally defined as two shots with a sight picture for both shots (sights, shot, sights, shot) followed by the follow-through sight picture. The shots are taken as rapidly as the shooter can acquire flash sight picture, with split times dependant on distance and shooter skill. Solid grip/stance will mitigate recoil, enabling the shooter to more rapidly acquire flash sight picture. The shooter will actively drive the sights for the second shot to ensure that correct sight picture is acquired before the second shot is fired. Split times will generally range from 0.30 to 0.60 sec with average-level shooters (more on this later), dependant on distance. Sight focus will also be dependant on distance, as the Controlled Pair is generally considered to be applicable from 15 yards to 50 yards with a rifle/carbine and 5 to 25 yards with a pistol, with the longer range shots (25+ for rifle, 15+ for pistol) having a target area of 8".
As people have begin to learn how to drive guns this method of delivery has become more and more the "way" to shoot pairs, especially with the evolution of the Modern Isoceles for pistol and an aggressive weight-forward rifle stance which permit the shooter to track the sights during recoil.

The Dedicated Pair. This is not a commonly referenced method, as it is somewhere inbetween the two. I believe it originated at Gunsight as people evolved the Weaver Grip into the "Modern Technique", which more effectively manages recoil. In the case of the Dedicated Pair the shooter can track the sights for both shots, but is applying the speed of the Hammer Pair, thus can see the sights align for both shots but is not correcting the flash sight picture for the second shot. The shooter can call the second shot, though it may or may not necessarily be within the targeted area.
Many people are shooting Dedicated Pairs thinking that they are shooting Controlled Pairs, accounting for poor shot placement on the second shot (rushing the second shot). Many proficient shooters are shooting Dedicated Pairs instead of either Hammer Pairs or Controlled pairs because their eyes are fast enough to track the sights and their grip and stance have become good enough that their sights do not deviate significantly from their initial aim-point during recovery (forecasting immediately acceptable sight picture).

There is also the possibility of simply taking two well-aimed shots. Generally any circumstance that causes the sights to be off of the target following recoil forces the shooter to break each shot down individually. If it takes more than 1 second to get the second shot off it is highly probable that the person you were shooting at will not be around for the second shot. This is in the context of longer distance shooting, outside the "knife-fight in a phone-booth" envelope that defines close-range gunfights. Traditional sight alignment and sight picture are required for these shots to ensure effectiveness. I include this note only to prevent the notion that firing any two shots with sight picture automotically includes it in the "Controlled Pair" category.

Now, these are simply defining the types of pairs. Actual application is something else entirely.

The leading IPSC/IDPA pistol shooters shoot aimed fire for each and every shot. Whether you define the shots as Controlled Pairs or Dedicated Pairs is irrelevant. They see what they need to see. Whether that means their level of focus on the sights or position of sight picture, they are not spending any more time on the shot than absolutely necessary to ensure that they hit what they need to hit. They are utilizing some method of aiming for the shots; those that shoot without aiming both shots do not become GMs. True, there are circumstances where they might not be using sights (rare as it is), they are still aiming each shot if only by controlling the gun, and know where the bullet is going before it gets there. For more depth on this read the thread by gotm4 HERE. While it is competition oriented it gives excellent insight into how GMs get to where they are.

While I do not use or advocate Hammer Pairs for pistols at distances where sights are necessary, I believe that they do have application for rifles/carbines. Long guns are easier to control for multiple successive shots at close range and are less apt to "slip" out of the target area as long as stance and grip are solid. The time that Hammer Pairs are most applicable is at 10-15 yards and under with magnified optics. The perceived bounce in the sights can cause the shooter to second-guess sight picture during recovery. I found that my Hammer Pair and Controlled Pair groups are virtually identical when pushing for maximum speed at close range (for me- 15 and in), and the Hammer gets it done in about 0.1 second faster. This means that I can transition to the next target(s) faster while still efficiently delivering damage to the initial target. That is not to say that everyone can do that, or that they can't do it at longer ranges than I can. It is simply my benchmark. With non-magnified optics I am content with Controlled Pairs and Dedicated Pairs since I have a solid fix on the dot and target throughout the pair process.

Really though, it doesn't matter what method you use or where your grey area is. What it comes down to is being accurate enough, fast enough. I would rather simply teach people how the methods work and let them figure out their own effective limits than force them to utilize a specific method at a specific distance. Of course I try to push people to become more accurate, faster; but not at the expense of hits. It doesn't matter how fast you pull the trigger, if the shots don't go where they need to go you are not effective. I personally believe that with a rifle/carbine it is imperitive to properly seat stance and grip, then move on to Controlled Pairs (permitting the shooter to build skill/confidence in utilizing the sights rapidly), and then to Hammer Pairs (builds off of Controlled Pair skills, but accelerates the second hit).

This is just my opinion, though it has been successful when training many people. I do not at all mean that this is the "one true path to tactical enlightenment", but rather an observation on the often misunderstood and misquoted "Double Tap" issue.

If I am wrong about the birth-place of any of these techniques or their reasons, I apologise and welcome any corrections. I wrote this from memory and could very well be wrong on who did what, when.

Just my .02 and 30 minutes.