First I want to discuss the uses and necessities of this. As I type, I have a Glock 17 Pistol in my belt. It has a threaded barrel, and an RMR (RM06)...but no weaponlight. Why not...don't ALL weapons need lights?
No, they do not. Let me restate that. Not all weapons need light, and specially not all pistols.
Ostensibly, the purpose for a weapon mounted light...or in this discussion, a pistol mounted light, is to identify the nature of a potential threat/target obscured by darkness. In other words, to give you more information than that which you are currently operating on.
A clear and present threat does not need to be identified any further. If you live alone and a large figure in moving down the darkened hallway telling you in an unfamiliar voice that he is going to kill you, you do not need to identify him before emptying your high capacity magazine into his face.
If in twilight, on a city street, a couple of bad guys "prison strut" over to you, with a "Yo motherf*cker!" while reaching for weapons behind their backs, you do not need to identify them any further either. Get my point?
The use of light is a proactive event. There is no tactical value for the reactive use of light. In a reactive event, you either see the threat and respond, or you are overtaken by the unseen threat. If you see the threat, you deal with it as you would during the brightness of the day. If you do not, it won't matter anyway.
The problem is when attorneys begin dictating tactics that things get weird and tactical mistakes are made. And of course...fortuitous outcomes reinforce bad tactics.
Light will not prevent an adversary from firing...no matter how bright it is. The notion that flashing a bad guy in the eye will somehow knock him down is a false belief. Sure, that may work with someone who really did not intend any harm, but not with a man whose intent was to take you out. So we must be very careful in its use and not think it is some sort of angelic shield that will save us from incoming fire. Light of course can be used proactively to mask your movement, but that is for another discussion.
So we begin the discussion of light from the proactive perspective. The mission requirements of the SWAT Operator may be different than that of the day-to-day UC Operative, or Private Citizen. BUT, when one is being PROACTIVE, the mission is identical. Lets recall that being proactive with a handgun involves defending a fixed location, or going on the hunt for the bad guy. We have discussed these strategies and tactics before, and they are detailed deeply in the DVD CQB Fighting In Structures.
So lets talk about the attributes of a weaponlight that best works in these situations.
1). It should be bright, but not excessively so. Bright enough to identify the concerns obscured by darkness sufficiently, but not so bright that it causes your eyes to squint. The tendency is "as bright as possible", but I think this is a mistake. I have not examined the new 500 lumens X-series from Surefire yet, but I suspect it may be too bright. We will see.
2). It MUST have a switch that allows for one handed use while you are shooting. Let me repeat that - WHILE YOU ARE SHOOTING. If you must use the support hand...or the trigger finger to operate the light, that light is useless in the tactical environment.
The reason is very simple. The handgun may need to be operated one handed. As a point of fact, that is its very purpose. So anything on the weapon must be operable with the shooting hand while the trigger finger is on the trigger. What does that say of some of the popular new "tactical lights" on the market?
The best of the breed are Streamlight and Surefire because they have the availability of the remote switching that allows for use by the firing hand, via pressure, while the finger is on the trigger. Incidentally, I use RTV to secure those remote grip switches to my weapons. I have seen these remote switches get hung up on gear and become disabled. Glue them down with RTV. That is Room Temperature Vulcanizing, a liquid rubber that solidifies in the air. I use it on my RMR screws as well.
The epitome of Night Fighting advancements are not in the brightness of the white light, but rather the proliferation of Night Vision Technology in the hands of the private citizen and individual police officer. As well, the development of the Non-military, EPA-approved, eye-safe (relatively) IR Laser. This brings the capabilities of the individual up to its highest developmental point yet in terms of operating in darkness.
The presence of night vision in the hands of the proactive good guy is a true game changer, and with the availability of the IR Laser, the game has become more one sided to those who wish to pay to play.
Recently, both Surefire and Streamlight have announced the availability of IR lasers to their pistol light series. These are not yet available, but when they are, I suggest them as a great piece of kit to add. The lasers are mounted in conjunction with the white light, and can be operated independently of each other. And most importantly, can be used with the remote switch to allow them to be deployed in a tactically correct manner.