Review: Surefire X400U-A-GN

The Surefire Surefire X400U-A-GN Weapon Mounted Light.
Whew!—that’s a full name isn’t it? Believe me, translated to English it’s much longer: “Pistol sized-but-appropriate-for-rifle Surefire High Lumen Weapon Light with Green Laser” (They’d probably run out of room on the box if they went with that).

Boring stuff out of the way first: So, we have a 500 lumen light and a 5mW green laser located directly below it. Beautifully hard anodized aerospace aluminum, waterproof, and rugged as hell… in other words: Standard Surefire build quality. Runtime is 1.5hours for the light itself.

Unlike your holy-shit-this-can-be-hard-to-put-on X300/U Surefire, the X400U-A-GN sports a slotted screw with a large head as opposed to the tight torture of the Surefire pull down and push. A medium sized screwdriver (or a multitool, or a coin) can be used to quickly attach it. For semi-permanent installation, such as on a carry gun, I suggest a small amount (like a drop) of blue loctite or similar thread locker on the threads to prevent loosening.

Grey Ghost Gear


Typical of Surefire, controls are entirely straight forward. Though the selection switch is marked it’s not entirely necessary because it’s incredibly intuitive. There is a lockout on either extreme (which is great for white light ND prevention) and it can be configured for light/laser combination, light only, or laser only. Once your selection is made, activation can be performed in several ways: For a momentary on, simply press the back of either paddle. For constant on, rotate the paddle in either direction. It’s entirely ambidextrous and light/laser attenuation is the same even when mounted upside down.

Zeroing requires the use of an included hex wrench that you will lose at least twice. No crazy science about this one. Adjust the laser to your POI at your desired range. Surefire claims that using Nylok screws means it will maintain zero and so far, in my experience it absolutely has. I’ve had it on pistols and rifles of several calibers with no discernable shift once zeroed (though it mostly stays on a fullsize 9mm Glock).

This Surefire is also compatible with pistol DG grip switches and rifle XT07 tape switches. Due to the laser diode, much to my dismay, you cannot run the X400U-A-GN in a Rhino WML configuration (my preference with the X300/U) without completely blocking your front sight.

“Did you know that the human eye can see shades of green more than any other color?”

There are about ten billion articles about green versus red lasers on the internet so I will only briefly cover this. Green lasers make for better daytime visibility even at extended ranges because green more prevalent in the human spectrum of sight (same reason many emergency vehicles are now green or yellow as opposed to classic red). It also means you pick the dot up faster. Of course, there are trade offs for this increase in visibility. Red lasers generally have a wider range of operating temperature. Green lasers are more expensive to make, and even more expensive to make durable, hence the increased prices that you see.

Book inspired gun porn

The same advantages and disadvantages of lasers on weapons still applies to the Surefire. It will not magically perform all of the necessary actions of trigger press nor correct your terrible flinch. Despite what the movies tell you, your shot won’t always go where the laser is because there’s still a lot you can dick up (and remember that a laser shoots out a straight beam, not a ballistic arc, so your POI will change accordingly relative to your zero).

However, it is still a useful training aid for tracking trigger pull. Any slight angular deviation with a weapon can translate to severe aiming shift at range. The further the range, the worse the shift. A laser demonstrates and can be used to correct shooting deficiencies.

Example of typical muzzle deviation when seen downrange


Lasers are also great for NPOA (Natural Point Of Aim) exercises. For mil/LEO use it can be used for escalation of force. Of course, I suppose you can also use it in situations where a traditional sight picture is otherwise impossible to take.

Regarding its use as a light, it’s a 500 lumen Surefire light. Brighter than I would like but something to keep in mind is, that while there are many ways to make a WML dimmer (translucent covers, flip caps, filters, and diffusers) there are none to make a light brighter. It uses a Surefire TIR lens which is suitable for close/mid work, which shouldn’t be a surprise, as it’s primarily for pistols.

One issue with having a [somewhat] nonstandard WML or other attachment is procuring a proper holster. If a rifle is wearing it, then it’s no issue. Thankfully, I have a Raven Concealment holster that accommodates the X400U. It well… works exactly like a Raven should: Awesome. Not too much commentary and no complaints on that end. In a world full of custom kydex, it shouldn’t be an insurmountable issue to have something made, just don’t expect to be able to walk into any country gun shop and automatically find your weapon/WML configuration on the shelf.

Raven Concealment Rig

Long story short: It works and works well. Takes a beating and holds a zero. If the Surefire X400U-A-GN checks the boxes that you need, by all means give it a go. The MSRP is $790 but they routinely can be found for considerably less.

Do you even Liberty 1



Some more articles that might interest you:

Concerns for WMLs – lights, mounts and features –

Graham Combat – fighting in low light.

Low light techniques for CCW:


About the author:A combat veteran of the United States Marine Corps, Mad Duo Dave Merrill is a former urban warfare and foreign weapons instructor for Coalition fighting men. An occasional competitive shooter, he has a strange Kalashnikov fetish the rest of the minions try to ignore. Dave is currently the operating manager and lead instructor for MilCopp Tactical. There he munificently promulgates superlative fighting advice. Translated, that means MilCopp teaches and advocates a constantly evolving, amalgamated method of military and law enforcement tactics,. They leaven those TTPs with lessons learned from continued training and ongoing experience on the sharp end; these TTP’s are based on a combination of hard lessons learned and practical real-world results. Merrill, who has superb taste in hats, has been published in a number of places, the most awesome of which is, of course, here at Breach-Bang-Clear. He holds the current world championship for kegel exercises and married way, way above his pay grade.

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