Flux Defense Equipped Glock — Ultimate PDW

I started a quest many moons ago for a Grail of sorts. What I would call the perfect “bag” gun. My hunt was for a Personal Defense Weapon (PDW) to meet my individual needs. I wanted something small and light enough to be easily carried in a discreet bag when out and about. Just in case. I intended it to be a complement to, rather than replacement for, my concealed carry piece. Why bother with such a piece? It would offer an increase in hit probability and extend the range over a traditional pistol, especially in the hands of your average shooter. By being concealed in a discreet bag, you could grab and sling it if you felt the need and go about your day. I envisioned it serving multiple purposes: PDW, backpacking/survival gun, small game hunting, and to stop an active shooter.

During my search, I came across Flux Defense’s Brace for a Glock pistol. As soon as I saw it I was intrigued by its possibilities, but I also had some doubts. So what exactly is the Flux Brace? Basically, it’s an easy to install stabilizing arm brace designed to be mounted onto certain Gen 3/4/5 Glock pistols. Flux also offers their Flashmag to complement it. This is a combination light mount and spare magazine carrier for a Gen 3/4/5 Glock pistol. Both of these units install easily with no gunsmithing required. Flux Defense now also offers a kit to retrofit a SIG Sauer M17/18 and P320 series, but I’ll focus on their Glock offering in this article.

Before I jump into Flux Defense’s brace though, let me share what I looked at prior to finding it. There are a number of off-­the-­shelf options, depending upon your size and weight requirements, suitable for carrying in some form of discreet bag. If you are willing to lug a messenger bag or pack capable of stowing something 19-­inches in length, you have a lot of options, including in rifle calibers. If you wish to move down to a smaller and more discreet bag capable of holding a firearm 16-­inches in overall length, your options decrease dramatically. Now, if you want to move even smaller, things begin to get much more difficult. I, of course, wanted smaller.

The “Grail” I was looking for would need to be compact enough, less than 12 inches in OAL, to store easily in a bag small and unobtrusive enough not to draw unwanted attention. Based on previous experience, I did not desire to always be saddled with something the size of a messenger bag. My goal was to find something small enough to fit into a bag of such reduced dimensions no one would suspect it of being capable of concealing a PDW. Close in importance to size is weight. The chosen piece, with associated optic, white light and loaded magazines, needs to be light enough to not become an undesired burden as you go about your day. If it adds too much weight and bulk, it will be left behind, simple as that.

Ideally, it would be quick into action, allowing you to draw and immediately engage a threat. If it has a stock or stabilizing brace, it should be designed to allow rapid deployment. Ideally, it will be equipped with an optic and white light enabling effective use in low/no light scenarios. Plus, due to the growing use of body armor by active shooters I would recommend having the capability of penetrating Level IIIA soft body armor. Accuracy wise, my goal would be for it to be capable of head shots from a supported position out to 100 yards.

During my initial search I came across a number of possible options. These included AR pistols with a side-­folding receiver extension, AR pistols with quick-­detach barrel assemblies, Zenith’s MP5 style pistol and SIG Sauer’s Rattler and Copperhead pistols to name some obvious examples. Of these options, my personal favorites were the Zenith built into a MP5K clone and SIG Sauer’s Rattler in 300 AAC BLK. While both are excellent options for many scenarios, I decided to look for something even smaller and lighter to give me an additional choice.

Enter the Flux Defense Brace for a Glock pistol. I do not think you can get much smaller than the package this provides with its level of performance. While the collapsible Flux Brace resembles a stock, it is NOT a stock and is not intended to be employed as a stock. Rather, it was designed to be utilized as a stabilizing brace, which when deployed can provide an additional point of contact. This can be either on the forearm or by the shooter placing their face against one of the steel struts. Similarly, the Flashmag light mount/spare magazine carrier was not designed to be, nor is intended to be, used as a vertical grip. There is more information concerning the legalities of the Flux Brace and Flashmag on the Flux Defense website and why they do not require an NFA tax stamp.

Unlike other designs, the Flux Brace is spring-­loaded and deploys from its collapsed storage position by merely depressing a release lever. To deploy the brace you simply push down on an ergonomic release with your trigger finger and it automatically shoots out and locks into place. The auto-­deploying capability reduces the time required to put the piece into action. There is no time wasted unfolding or extending a brace or stock. Once the pistol is clear of the bag you simply depress the release and the brace snaps out as you bring the pistol up. It’s slick. Distance from the rear of the brace to the trigger is approximately 12.2 inches.

The Flashmag is designed to hold an Olight S1R II Gen II 1,000 lumen flashlight. This adds white light capability for use in low light and no light scenarios. Having a white light is a must have in my book. The light’s activation switch is located on the left side of the Flashmag and the light can be recharged without having to remove it. Plus, the Flashmag can hold one spare magazine. This is retained by tabs which engage into the slots on the magazine body. This provides the ability to have a reload ready to go on the pistol.

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Installing both units is very simple and straight-­forward, no gunsmithing or odd tools required. The Flux Brace simply slides onto the rear of the Glock’s frame and is secured into place with one cross-­pin. Tap the pin into place and you are done. The Flashmag slides onto the dustcover’s rail and is secured with one cross-­bolt. This is again very quick and easy. Installing both units takes only a couple minutes.

I mounted the Flux Brace and Flashmag onto a Glock 35 Gen 4 MOS I purchased specifically for testing. Why a Glock 35? For two important reasons, I wanted the extra barrel length and because it allowed me to easily convert from .40 S&W to 9mm Parabellum and .357 SIG. Each one of these calibers brings something to the table and the additional barrel length would aid velocity. Next I purchased a standard length 9mm Parabellum barrel and an extended threaded .357 SIG barrel from Lone Wolf Distributors. Both were from their Alpha Wolf line with the 9mm conversion barrel costing me $139.95 and the extended and threaded .357 SIG conversion barrel a bit more at $159.95. I added a fourth caliber into the mix with a Tactical Solutions’ TSG-­22 17/22 .22 LR conversion kit. Now I had one pistol capable of being quickly and easily converted to fire four very different calibers.

The next step was to decide on a sighting system. I replaced the factory plastic sights with a set of simple black steel suppressor height sights. The big question though was what to select for a red dot sight. I believe a red dot is required to extract the maximum potential from a set-­up like this. While a conventional square notch or “U” notch iron rear sight works fine when the pistol is held at arm’s length, it’s much harder to use when the pistol is held close to the face. This is due to your eye not being able to focus this close. The rear sight simply blurs out making correct alignment very difficult. A micro red dot on the other hand works perfectly.

For a sighting system I initially selected a Trijicon RMR RM07 Type 2 with a 6.5 MOA dot I had on another pistol. The large dot size is easy to see and quick to pick up. It’s fast and works well, but as distances grow it does become a bit big, especially when you stretch out to 100 yards. After using it for a bit on the range I purchased a Trijicon RM06 with its smaller 3.2 MOA dot. In use the smaller dot did prove easier to use past 50 yards while also aiding precision. A screw kit is required for mounting an RMR onto the Glock MOS, so I purchased that as well from Trijicon.

The resulting package with the standard length barrel and the Flux Brace collapsed measures just 10.3 inches in length. Hit the button and extend the brace and the package grows to 17.5 inches. Installing the extended .357 SIG barrel brings it to 10.7 inches. Adding a dual baffle muzzle brake to the .357 SIG barrel brings it to 11.6 inches, and 18.75 inches with the brace extended. That is short. So, I was able to go even shorter than my original goal of 12 inches. Better still, it weighs in at only 2.5 pounds. This size and weight are ideal for my needs. Handling is very good with it proving to be very quick and nimble. Being so small, it tucks away easily until needed.

There are a few things to be aware of though. Adding the brace does change how the pistol feels and will slightly hinder your access to the controls. As the brace tucks in beneath the travel plane of the slide, it will lower your grip. With the brace collapsed I cannot access either the slide catch or magazine release with my firing hand. I can easily access both controls with my non-­firing hand, but it’s something to be aware of. My solution to this is to just deploy the brace on the draw. As the pistol is drawn, trigger finger is straight, once the pistol is clear of the bag the trigger fingers moves up slightly and depresses the release auto-­deploying the brace.

With the brace deployed I can access and manipulate both the slide catch and magazine release by slightly pivoting the pistol in my hand. The controls can also be easily manipulated using the non-­firing hand. I spent some time on the range and quickly came up with procedures to easily and effectively run the pistol. The learning curve is slight, I had no issues with it, but it is something to be aware of.

Now, keep in mind, this does not replace the concealed carry pistol I carry every day. It is meant as a step-­up from it for when the situation allows. Close, immediate threats would be engaged with my concealed carry pistol just as you would expect. If given the time and opportunity to draw and deploy the Flux Defense equipped Glock 35 MOS, I now have a more capable piece.

The Gen 4 Glock 35 MOS used for testing was totally stock, just the way I took it home from my dealer. The only exception being the aftermarket barrels utilized. The trigger is typical standard Glock and nothing to write home about. The MOS system utilizes a plate system which sandwiches between the red dot and the pistol. This is certainly not one of Glock’s better ideas. Some owners have experienced the screws loosening and the sights suddenly starting to wobble. I used a goodly amount of thread-­locker and have never experienced an issue with this particular pistol, but did have it happen to me with a demo gun at an industry event. It’s just something to be aware of.

I purchased the Gen 4 model for one reason, at the time Flux Defense only offered their brace for Gen 4/5 pistols. Now they offer them for the Gen 3 models as well. While I like the upgraded recoil spring assembly of the Gen 4 Glock, nothing else I see would lead me to cast aside my Gen 3 guns. I don’t think the changes warrant it, but your opinion/needs might be different.

The big question is, how much of an aid is it regarding hit probability and extending practical reach over my normal concealed carry pistol? To find out, I spent a considerable amount of time on the range over a few months’ time. I began testing by getting a rough zero and checking Point of Impact at 50 yards. Then I started shooting groups from the bench with the 9mm Alpha Wolf conversion barrel. Four five-­shot groups were fired from a rest at 50 yards using four different loads. These consisted of Black Hills Ammunition’s 115-­grain Tac-­XP +P solid copper HP, Fort Scott’s 80-­grain monolithic solid, Barnaul’s 115-­grain FMJ and SIG Sauer’s 365 V-­Crown 115-­grain JHP.

To be blunt, I wasn’t really sure what to expect from the Alpha Wolf barrel. It’s not particularly expensive, but this individual barrel performed better than anticipated. Best accuracy at 50 yards was obtained using SIG Sauer’s 115-­grain V-­Crown JHP which averaged an impressive 2.6 inches at 1,237 fps. Black Hills’ 115-­grain Tac-­XP +P load printed almost identical size groups averaging a note-­worthy 2.7 inches at 1,255 fps. Barnaul’s economical steel case 115-­grain FMJ was the real surprise, averaging 3.7 inches at 1,194 fps. Fort Scott’s 80-­grain Solid Copper Spun monolithic solid posted a respectable 5.1 inches at 1,491 fps. When the last 9mm empty hit the ground the Glock 35 MOS with Flux Brace had performed better than expected.

Swapping the barrel out, I switched to .357 SIG. Testing was conducted using four loads ranging in weight from 65 to 135 grains. Whereas the Glock was very pleasant to fire in 9mm Parabellum it became a bit of a handful with certain loads in .357 SIG. This increased split times between shots when trying to shoot fast. After mulling this over a bit, I purchased an inexpensive aluminum dual-­baffle muzzle brake which noticeably reduced recoil and muzzle-­rise. Unfortunately, testing revealed that it also introduced vertical stringing with all the loads except the Lehigh Defense 65-­grain Xtreme Defender. So, it was removed for accuracy testing with all loads except the Lehigh Defense.

The Alpha Wolf .357 SIG conversion barrel didn’t prove to be quite as accurate as the 9mm Alpha Wolf barrel. Even so, it shot acceptably well. Best accuracy was obtained using the Lehigh Defense 65-­grain Xtreme Defender load with the muzzle brake attached. It averaged a respectable four inches, at a blistering 2,109 fps. Without the brake, the Lehigh Defense load strung vertically in the seven-­inch range. Recoil was mild. With the muzzle brake removed the Hornady 135-­grain Critical Duty averaged 4.2 inches at 1,332 fps and the Fort Scott 95-­grain Solid Copper Spun averaged 4.3 inches at 1,790 fps. The SIG Sauer 125-­grain V-­Crown JHP opened up to 7.5-­inches at 1,479 fps. This load was a thumper!

Since the 9mm Alpha Wolf barrel grouped the tightest, I switched back over to it. Then I moved the target frame to 100 yards. This is the furthest I would anticipate employing the Glock 35 MOS, so was itching to see how it would perform. At this longer distance Black Hills Ammunition’s 115-­grain +P Tac-­XP took top spot. Six five-­shot groups fired from a rest averaged a surprising 4.8 inches. SIG Sauer’s 115-­grain V-­Crown averaged 5.8 inches while Barnaul’s 115-­grain FMJ averaged 6.5 inches. At this distance Fort Scott’s 80-­grain load opened up enough I dropped it from testing.

Once again the .357 SIG barrel didn’t perform as well as the 9mm barrel. I fired three .357 SIG loads at 100 yards. The Lehigh Defense 65-­grain Xtreme Defender averaged eight inches, the Hornady 135-­grain Critical Duty averaged 8.5 inches and the Fort Scott 95-­grain solid averaged nine inches. While the .357 SIG would easily stay on the chest of a man-­sized target at 100 yards, the results were not as impressive.

Swapping back to 9mm, I moved from the bench to firing prone, kneeling, supported off a barricade and standing at 100 yards. Firing prone, and off a barricade, I was able to consistently keep all my shots from a five-­round string on an eight-­inch plate using the Black Hills 115-­grain Tac-­XP load. Place the dot on top of the plate and I was rewarded with a satisfying smack! Making fast center hits on a steel silhouette from the other positions was relatively easy. Take your time, carefully press the trigger and focus on the fundamentals and the Flux equipped Glock would ring the steel every time.

Moving to 75 and then 50 yards and things became easy. At 50 yards you can make very fast multiple hits on a silhouette, or multiple silhouettes. In my opinion it gives up very little to my MP5K PDW clone, while being substantially smaller and lighter. I took a bit of time figuring out the best way to draw the Flux equipped Glock from a bag, and quickly put it into action while moving off the “X”. Through-­out testing the Glock 35 MOS proved very reliable, magazines locked into place without issue, the controls functioned as they should and feeding and ejection was excellent. The Trijicon RMR definitely aids accuracy and speed, especially as the distance to the target grows.

I mentioned earlier the desirability of defeating Level IIIA body armor. This is due to its use by active shooters in recent years, and the probability of encountering it being worn in such a situation. Many recent active shooters have donned body armor before beginning their hate fueled shooting sprees. While there are commercial off the shelf loads in 9mm Parabellum and .357 SIG which will penetrate Level IIIA body armor, most will not. Many loads you would expect to will not. For example, the Lehigh Defense .357 SIG 65-­grain Xtreme Defender is a monolithic copper solid with rifle like velocity.

On paper it appears it should penetrate soft body armor due to its construction and velocity. I then tested it against a Level IIIA soft body armor panel from BulletSafe. This Level IIIA vest is priced at $299. Testing was conducted at 12 feet with one shot to the center of the properly backed-­up vest. The vest stopped it cold, mainly due to the nose design of the projectile and the construction of the body armor panel. Back-­face deformation was severe and the projectile came close to penetrating. However, while exceeding this vest’s specifications, this load was defeated. Just food for thought.

I also did some limited testing with the Tactical Solutions’ TSG-­22 17/22 .22 LR conversion kit. This is a good looking piece which installed easily taking the place of the standard slide assembly. It takes less than a minute to convert to .22 LR. It features a steel slide and a threaded barrel is an option. I added a SureFire Ryder .22 LR sound suppressor and it proved both reliable and fun. I didn’t have a chance to conduct formal accuracy testing with it, but running it on steel plates and a dueling-­tree revealed it to be accurate enough for small game hunting. It would make a useful “survival gun” or game-­getter in .22 LR, although it would benefit from a red dot.

Throughout testing I had exactly one issue. One round of Fort Scott 9mm failed to eject. It felt a bit light when it went off and the chronograph revealed a velocity almost 200 fps lower than the rest. Other than that, the Glock functioned without incident. The Flux Brace functioned perfectly and proved more robust than expected. I really like it. On the flip side, I don’t like or recommend the Olight S1R II flashlight for tactical use. I employed it running drills in low light and no light scenarios and found it very wanting. This is due to the switch and how the light itself functions. For those not satisfied with the Olight S1R II light, Flux Defense does offer an option. They introduced a new model with a 1913 rail for mounting standard pistol lights while retaining the spare mag carrier. I have not handled this piece though, so cannot comment on it.

I did like the spare mag carrier portion of the Flashmag. It works well and provided a quick reload. It retained all the magazines I tried, except a fully loaded 33-­round 9mm, securely. The 33-­round magazines simply proved too heavy and could fall out under energetic movements. I performed tactical reloads with it where the partially expended magazine was inserted into the mag carrier following the reload. This worked well, and kept the partial mag ready if needed.

All in all I am very happy with my PDW build using the Glock 35 MOS, Alpha Wolf barrels and Flux Defense Brace and Flashmag. After testing both .357 SIG and 9mm Parabellum I think I will use it mostly in 9mm. While a PDW like this is certainly not for everyone, it meets my needs and will nicely compliment my Rattler and MP5K clone. Price is $259 for the Flux Brace and $79 for the Flashmag while the Tactical Solutions .22 LR conversion kit is $399.

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