It seems that lessons need to be continually relearned because either they were never learned in the first place, or they were quickly forgotten due to inconvenience. The topic is weapon lights...and pistol lights in particular.
They look very dramatic on those custom handguns in photos. We need to ask why they are there, and secondly if they are an asset on every single weapon. To answer the unasked question about my perspective and authority, all but one of the dozen gunfights I was involved with were in reduced light.
The first issue is that if you do add a light, you need to know how to use it. I am always concerned about drawing fire by using a light excessively or inappropriately. If there was no concern over such things, we would simply turn the light on and leave it on like they do on TV Cop shows. I expect that most guys that add a light to their pistol, rifle or shotgun, will do just this and then vociferously defend their tactics online. The problem is that all their experience comes from shooting ranges, gun games, or extremely one sided engagements.
They are wrong and it will eventually get them killed.
I teach to refrain from using the light as much as possible and only use it when absolutely necessary. And that "necessary" occurs only when there is doubt about what the target is. We do not need as much "Target ID" as the Liability-Mongers would have you believe.
For example...if I see a 6 foot tall 200 pound shadow in my home at zero-dark-thirty, I am safe in assuming that is an enemy invader and I will shoot him to the ground since nobody that lives with me is 6 feet tall and 200 pounds.
I have all the target ID I need. Feel free to seek more if you must, but if you have raised your family correctly, and locked your doors, you will not need to do so. Understand that if it was truly a violent armed criminal and you turned on your light, he will shoot at your light. I know I would. There are tactics to use the light properly that mitigate the danger of turning it on, but for now understand that when the light is on you are a target. Whether the enemy shoots you or not is his choice...not yours.
I have a Surefire weapon light on my Home Defense Weapons (just like I used in SWAT although vastly improved) because all Proactive CQB Weapons should have a light. Did you catch the qualifier adjectives? "Proactive" and "CQB". I did not say "All Weapons".
Weapons that are reactive in purpose do not require nor do they benefit from adding a light. Move through the urban night environment and you will see that short of a black out (which would require a light to navigate), there is always sufficient ambient light to recognize a pending threat or upcoming attack. There is no tactical scenario that I can envision where one would need to reactively illuminate a threat prior to shooting.
The companies that make weapon lights have a vested interest in convincing the public that all weapons need lights, and that nobody should ever carry a weapon without a light. That is great for sales but not the best choice for everyone else. So "some weapons and tactical applications" benefit from having a light mounted...others do not.
The second important point is that if you are mounting a light on a pistol, it must be operable with the shooting hand, and while the trigger finger is on the trigger. If you cannot operate the light, in a pressure activated momentary manner with your shooting hand only, and while your trigger finger is on the trigger, it is a stupid accessory and does not belong on the weapon of a serious gunfight-focused shooter.
This is a good choice. See the grip activated pressure switch?
This is a poor choice. There is no way the user will be able to activate the light, one handed, while the trigger finger is on the trigger.
If you must take your trigger finger off the trigger to turn on the light, or the light is designed to be turned on, and then left on mechanically as you shoot, it is a poor choice and virtually useless for any real world uses.
To use a light on a pistol properly, it must be used with a momentary pressure switch. Add pressure and the light turns on. Remove or relax pressure and the light turns off. I want to be able to illuminate a threat with that pistol light, via grip pressure while my finger is in contact with the trigger.
Having to use my trigger finger or the fingers of my support hand to operate the light is unsatisfactory.
There will be many times when you may need to let go of the pistol with your support hand to open a door, or move with stealth in the dark (which is why we are talking lights in the first place). You illuminate that corner that contains the threat, but you are doing so with your trigger finger. Now it is time to shoot. Do you let go of the momentary light switch to go to the trigger in darkness?
Think the matter through and you will arrive at my same conclusions.