The Ultimate Guide to Weapon-Mounted Lights

Weapon-mounted lights have become increasingly popular on modern firearms due to their improved power and general usefulness for defensive shooting. The prevalence of modern guns has made them easier to access and utilize. While weapon lights are a seemingly simple tool, there is a lot to consider when it comes to choosing and employing one. We are going to break it down piece by piece.

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The name is pretty straightforward, but if you’re like me and ate crayons for a few years, it’s good to have a solid definition we can all agree on. A weapon-mounted light (WML) is a flashlight that attaches to a firearm for the purpose of establishing positive identification of a target or non-target.

The golden question is, “Do you need one?” As always, the situation will dictate the need for any tool, and “need” can be a strong term. For home defense and duty users, a WML is a competent tool. In terms of need, I do think home defenders and duty users should seriously consider a weapon-mounted light.

For concealed carry, the term “need” tends to be pretty strong. While useful, it’s not necessary, and it’s typically easier to carry a handheld light than to attach a light to your handgun. The presence of a WML does not remove the need for a handheld light.

The main advantage of a weapon-mounted light is the ability to maintain a two-handed grip on your firearm, which provides better stability and increased accuracy. It’s typically faster to deploy since the light is drawn with the gun.

The big downside is muzzle awareness. Shooters can fall into a habit of pointing their light while failing to remember they are pointing their gun at it. You have to maintain excellent muzzle awareness when using a WML.

As with everything, proper training and practice are critical for utilizing a weapon-mounted light.

When employing a WML, you must understand its purpose. These are tools used to aim and establish positive identification. It’s not designed for constant searching or to find your keys. Good tactics can allow your weapon-mounted light to bounce light off reflective surfaces and use it for some search functions, but that’s not the primary purpose.

When shopping for any light, you’ll be hit with lots of numbers and terms. These terms are used to explain a light’s power, but also to market the light. It’s wise to understand these numbers and the story they tell.

Lumens is the term that’s most prominent in light advertising. This is the measure of how much light is being generated. The higher the number, the brighter the light. For a long time, there were the “lumen wars,” which were light companies trying to out-lumen each other, but the conversation has shifted.

The conversation is now focused on candela and lumens. Candela measures the intensity of the light in a specific direction. Lumens are the light’s brightness, and candela is the light’s ability to push that light forward. A mix of candela and lumens may call for fewer lumens and more candela.

We don’t see the term lux mentioned much anymore, but lux measures how lumens land on a specific area. One lux is equal to one lumen spread out over one square meter. Lux level is dependent on both lumen output and distance from the target.

This term applies to how far the light can go and still be effective. Most light companies will provide a beam distance that seems quite far. That’s as far as the beam can travel, but throw is how far the light can travel while remaining useful. Throw is determined by candela and reflector design.

High-throw lights act as a spotlight, while low-throw lights act as a floodlight. There are some benefits to both designs. For indoor use, a floodlight beam fills your field of view. High-throw spotlights are useful outdoors when distance is king. Certain platforms benefit more from specific types of throw based on their effective range.

A hot spot is the brightest part of the light. It sits at the center and is the concentrated part of the beam. The hot spot is where your focus is put when using a weapon-mounted light.

Spill is the area around a hot spot. It is less intense but provides peripheral vision illumination to see a wider area around the hot spot.

Corona is the portion of the light’s beam that sits between the hotspot and the spill. It’s a small ring of light that’s brighter than the spill but dimmer than the hotspot.

The hotspot, corona, and spill of the light come down to the light’s reflector. If you look into the front of a light (make sure it’s off, fellow crayon eaters), you’ll see the bulb and a shiny reflective surface. That shiny surface is the reflector.

Reflectors are what direct light forward. The shape and texture of the reflector are key to creating a light’s distinct beam. Most weapon lights will have a purpose-built reflector designed to propel light further and ensure a particular hot spot.

Temperature doesn’t refer to the light’s heat. Powerful weapon lights get hot, and most even have a warning. Temperature, when we talk about light, refers to the light’s hue. Temperature is a spectrum and is measured using Kelvin.

A low kelvin, or low-temperature light, gives you a warm, yellowish light. Mid-range temperature lights are typically neutral white lights. High kelvin numbers have a bluish tint.

Temperature matters when it comes to being able to determine colors. Warm or cold lights can affect your ability to perceive specific colors.

WMLs can often have a multitude of modes that determine how you can use the light. A variety of modes allows you to tactically employ the light most advantageously. Most weapon lights are pretty simple and typically have one to three modes. Your tactics and situation will dictate which mode is employed.

Constant is the most common mode you’ll find across any form of flashlight. When you hit the button, the light comes on and stays on until you turn it off. This constant mode is often employed when aiming at a fixed threat or target. It can also be used to provide light to clear complicated malfunctions.

Momentary modes allow you to activate the light for only as long as you need. Typically, a momentary mode will activate as long as the activation device is held down. When released, the light will automatically shut off. Momentary is used to avoid having the light constantly on and to prevent potential threats from tracking your light. It’s for situations requiring brief illumination to identify obstacles and threats.

Strobe modes are the constant on and off of a light. This mode is typically used to disorient a threat and help disguise the user’s position while illuminating the danger. The use of strobe has largely fallen out of favor on weapon-mounted lights and in modern tactics, although many will still feature the mode.

Some lights will allow the user to control the lumens and candela generated by the light. This is commonly referred to as high and low modes. This can help preserve battery, as well as allow the user to prevent reflections of light that can disorient them in some environments.

Just as we accept a diversity in firearm design with rifles, shotguns, and handguns, there are different light designs for these platforms.

The differences will be in size, activation method, and mounting method. Some lights can cross-pollinate between different guns. For example, a pistol light can fit on a shotgun or rifle easily. Is it the best option? Possibly, depending on the light and the gun’s purpose.

However, rifle lights aren’t going to work well on pistols due to their size and attachment method. Those same lights might work well on shotguns, but on pump shotguns, a dedicated shotgun light might be the best option.

A pistol light might be perfect for a Glock 17, but it would be much too large for a Glock 43X. As always, consider the gun’s purpose and task when outfitting it with a weapon-mounted light.

How the light turns on is a matter of ergonomics, and it can be a critical consideration. Understanding a light’s controls can be a helpful way to pick the light that’s perfect for you. 

Switches are typical on handgun lights. They flip up and down to activate the light. These switches can be a fast way to turn the light on and off and activate momentary modes. 

Clicky tail cap is a very scientific way to describe the button that sits on the back of long gun lights. This is often the default activation method on long gun lights. Clicky comes into play because that’s the audible and tactile response you receive from pressing the button. 

On shorter guns where a pressure switch isn’t needed, a tail cap makes for an ergonomic way to activate a light. 

Pressure switches are common on long gun lights. They will replace or augment a tail cap switch. A pressure switch connects to the light via a cable and then positions a switch behind the light. The cable allows the user to position the switch wherever they want it on their handguard or firearm. 

The switch then activates the light with ease. This can be handy when using a standard rifle or carbine. You can position the light far forward and still activate it with a natural firing grip. 

Pad-style activation switches are not the common way to activate a light. These pad-type buttons are integrated into the light and provide a large, easy-to-engage way to turn the light on. Pads can provide multiple ways to activate the light, like the Surefire DSF, which provides individual pads for momentary and constant modes. 

Lights like the Streamlight TL RM2 or Inforce series use pads to control the entire light, which can also provide constant or momentary modes via long and short presses. Pads can be an excellent and ergonomic way to activate lights on short platforms like PDWs, subguns, and similar weapons.  

Let’s put the “mounted” in a weapon-mounted light. Mounting systems vary, but tend to be fairly standard amongst gun companies and weapon light companies. 

Rail is an incredibly common way to mount any firearm accessory. Nearly every modern handgun has a rail. Shotguns and rifles can be outfitted with rails to mount lights. Rail systems provide a simple, common, and easy-to-use mounting system. 

With handguns, there can be some variance between rails. This can be due to length, rail slots, and the size of the gun. Most companies feature modular rail keys to accommodate a variety of different weapons. 

Some companies have proprietary rails. For example, some HK weapons like the USP have a proprietary rail that may require an adapter to fully function. 

For long guns, M-LOK and keyMod systems provide a direct mounting system that doesn’t need a rail. Instead, the light mounts to a slot and is secured by a T-shaped nut. The benefit of these modular systems is less bulk, less weight, and more positional opportunities for the light. Modular handguards can allow for a streamlined setup for long guns. 

An older, but still common enough way to mount lights to a shotgun is via a barrel and a magazine tube clamp. These attach to the barrel and magazine tube and can provide a rail or even an M-LOK slot to allow you to mount a light. 

While uncommon, there are weapon lights designed for smaller firearms that might lack rails. These latch the light around the trigger guard. It becomes a semi-permanent attachment at that point.  

You can’t have a light without batteries. With weapon-mounted lights, you’ll find a diverse set of battery options. There are some general rules of thumb when it comes to batteries and WMLs. First, always use good-quality batteries to get the most light and battery life possible.

Additionally, quality batteries are less likely to leak or break under recoil. Always pay attention to the manufacturer’s recommendations for batteries. Just because a battery fits doesn’t mean you should use it.

Speaking of recoil, shotguns can be hell on batteries. Recoil can break batteries, but not quickly. If you train with a shotgun and fire dozens of rounds, it might be an issue. I suggest removing light batteries if you’re not training with a shotgun in low-light conditions.

When choosing a light, pay attention to the batteries required and make sure they are widely available and not priced out of your budget.

Some lights use rechargeable batteries, others use disposable batteries, and some can use both. Modern rechargeable batteries can hold more “juice” than disposable batteries. They are more expensive, and while useful, once they die, you either need a second rechargeable on hand or you’re out of luck.

Disposable batteries allow for quick and easy “hot swaps” in the field. It’s cheaper to purchase multiple disposable batteries and keep a stash on hand. Plus, if you tend to forget to recharge batteries, these can be more useful.

There are also fixed or proprietary battery systems that, while rechargeable, can be a hassle. Olight famously uses fixed batteries, and while they work, when they degrade, your light becomes a paperweight.

Other systems, like the Surefire XSC, use a removable proprietary battery, which locks you into one company for support.

Dual-fuel designs can refer to a light capable of using multiple battery types, like AAs and CR123s, or rechargeable and non-rechargeable. This can simplify logistics and help you power your light in multiple situations.

When using dual-fuel designs, be aware of power changes. Some lights may emit lower power when paired with certain battery types. There can be a drop in lumens and candela with certain battery types.

When using rechargeable batteries like 18650s, you must use protected batteries. These batteries feature a small internal circuit board that acts as a safeguard. This prevents overcharge, over-discharge, short circuit, and overcurrents.

Protected batteries can protect your light, which is already an expensive investment.

When it comes to weapon lights, there are a lot of little considerations you have to make. Most of these don’t belong in a particular section, but still deserve mentioning. This is the leftovers, if you will.

If you’re equipping a handgun with a weapon-mounted light, you need to consider a holster. Depending on the gun and the light, finding a holster might prove difficult. You have to keep this in mind when shopping for a weapon light for your gun. Without a holster, a handgun isn’t all that useful outside of home defense.

Barrel Shadow

Barrel shadow occurs when your light sits behind the barrel, or under it. The light creates a shadow, which gives you a blind spot in your light’s beam. Depending on your setup, you can work to eliminate barrel shadow or reduce it. It takes some configuration, but it’s not a major problem.

Weapon lights typically sit close to the end of the barrel. As such, they get really dirty from carbon. When a light gets dirty, its performance is compromised. After shooting, you should clean the light. If you have a long day of training, this can be more difficult, but there are dedicated lens cleaners. 

These can make it easy to clean your lights. If you know you’re going to be training and shooting a lot, you can apply Chapstick to the front lens, and then at the end of the day, wipe it off.

READ MORE HERE: Symbiote Night Vision & Thermal Bridge Review

Weapon-mounted lights are becoming more and more common. More companies are producing more lights; some are great, others not so much. With that said, weapon lights are an investment, and like any investment, you should do some research into your light and consider your weapon and how you plan to use it.

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