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Flux Defense MP17 Gen II Raider

We’ve covered Flux Defense before, the Utah upstart that made a spring-loaded Glock brace that snicked out like a switchblade. Even if you didn’t like it, you still liked it because it just oozed cool. They followed that up with their take on an American-made B&T USW, the MP17 (See CONCEALMENT Issue 16 for a full review). This is Flux Defense’s MP17 MkII, aka the Raider. As the name implies, it’s meant to be light, fast, and quick into action. 

A quick glance reveals no obvious differences between the original Flux Defense MP17 and the Raider, but of course and as usual, the devil is in the details. A closer look at the surface texture of the original MP17 betrays the fact they were 3D printed — which by itself is perfectly fine. We’ve seen 3D printers produce everything from AR lowers to enhanced controls and even silencers. That said, the Raider is injection-molded plastic and of sufficient quality as to not split apart in layers like so much PLA. 

Flux defense Mp17 raider
A standard weapon-mounted light does make the Raider a bit harder to shoot but the additional functionality is worth it.

The manufacturing method itself is worthy of a new line, but we’ll be covering other changes as we come across them and there are some major ones. 


Before we dive further, we have to talk about braces themselves. At the time of this writing, President Biden just gave his first speech about his desire to restrict the use of so-called “pistol braces.” Between now and when you read these words there may undoubtedly be changes. We covered the previous internal memos used to determine intent in CONCEALMENT Issue 19, but the short story is this: We rolled with a chassis that was already registered as an SBR to avoid any issues. Flux Defense will also release an SBR version in the relative near future. With that in mind, we’ll use the terms “brace” and “stock” interchangeably in this piece. 

ATF pistol Brace Ban Cover

See RECOIL Issue 44 or for information on how to complete your own Form 1 SBR. 

Read ATF Pistol Brace Ban to see what's proposed and what you can do about it.


The optic mount of the Flux Defense MP17 was a universal-type plate without any accommodation for additional posts or recoil bosses. With the Raider, Flux instead opted for a plastic Picatinny rail for mounting optics. While this is clearly a more user-friendly approach, plastic mounting solutions don’t exactly fill our hearts with confidence. We realize we’re not talking about a precision rifle, but instead a more-capable pistol, but we’d like to see an approach closer to an OuterImpact or Strike Industries universal plate. 

Flux Defense MP17 plate
The original MP17 (top) had a universal MRDS plate but the Raider (bottom) has a three-slot Picatinny rail. The iron sights are still accessible.

The Picatinny rail does add some height over bore, but in this case it’s actually a positive. When you only have a short length of pull to accomplish “brace-length” status, a higher-mounted optic is actually more comfortable. The additional added height of the rail makes this even easier, but you may run out of vertical adjustment before you get your zero with some optics. 

flux defense mp17 iron sights
Oh yes, and you can use your BUIS in an emergency too if need be. 

The polymer Picatinny rail also only has three slots; many MRDS Pic adapters require four to properly lock in, so be choosey. 


Here’s where we see some significant deviations from both the Flux Defense MP17 predecessor and also the original P320.

Flux Defense MP17
Top: Gen 1, Bottom: Gen 2 Raider

To deploy the brace of the Raider, a lever on the right side needs to be depressed, and it extends automatically. If for some reason you don’t receive a full deployment (like it catches on your shirt — ask us why we know), you can manually retract it. To replace, press down once again on that forward lever and press in the brace until you hear and feel the audible click of the locking mechanism. 

flux defense mp17 raider safety
The Raider comes equipped with a chunky, removable, lever-type safety that works with any P320 chassis — though we recommend against doubling up.

While the original Flux Defense MP17 had cutouts for the optional use of a P320 FCU with a manual safety selector, there are no such holes on the Raider; that said, the impressions remain for those who believe in Dremel-thaumaturgy. As it ships, if you want a Dremel-free installation of your manual safety FCU, you’ll have to replace the safety with a $15 pin. 

flux defense mp17 gen ii brace
The spring-loaded brace snicks out with a quick push of the deployment lever. Sorry, left-handers.

Flux Defense instead opted for their own safety selector, a lever this time instead of the complicated crossbar mechanism of the original MP17. Though the safety is intuitive, we didn’t find it especially comfortable or ergonomic. All told, we prefer a normal manual safety that can be manipulated with the support-hand thumb — or so we thought.  

The original M17 used a simple press-fit for the spare magazine that would’ve inevitably been subject to wear. Not so with the Raider. There are a myriad of ways to drop both the primary and spare magazine of the Raider. A push-button primary magazine release button is located on the right-side of the chassis that can easily be hit with your trigger finger à la an AR-15. You can also reach up and push a spring steel lever forward with your shooting thumb to drop your primary magazine. Finally, a push-button on the back of the spare magazine holder can be used to remove both: a half press removes only the spare, while a full press drops both. It’s slicker than snot if you can pull it off and makes for a damned funny show if you don’t. 

flux defense mp17 raider mag release
There are three ways to release magazines with the Raider. A push-button on the right, a thumb release along the bottom, and a sliding mechanism on the left. No one will be hurting for a lack of options, but we suggest you find the one you like and just stick to it.

For changing magazines in a flash, this was our preferred method: wrap the fingers of your support hand around the spare mag holder. Using the thumb of your support hand, press the button in far enough to remove both magazines. Allow the primary magazine to drop while you swap in the secondary. 

Without an extended slide stop lever or a forward charging handle, it can be kind of a pain to lock the slide back on the Raider. We received a preproduction charging handle from another company that fits into the front sight dovetail — but broke it almost immediately (thus the nature of preproduction parts). However, by the time of publishing, there may be more than one viable charging handle available. Until that time, we’re just grabbing the front of the serrated Grey Ghost Precision slide for nearly all of our manipulations. 


In one hand, we have a brand-new SIG Custom Works FCU; in the other, we have an M17 FCU with a manual safety that’s already been registered as an SBR, so we have options. We can all the parts between the two sans the skeleton, remove the manual safety of the M17, register the new FCU, or grind on the Raider. We decided on the Dremel, but all told we’d have done better just to spend an additional $200. How many SBRs is enough? At least one more. 

flux defense mp17 raider

For the optic, we decided on the new SIG Romeo2. The Romeo2 is SIG’s latest answer to the clamoring for a sealed reflex sight. It can be run as an open emitter, a shielded open emitter, or a completely sealed sight. This hybrid unit mounts on a standard SIG P320 footprint as well as a Leupold Delta Point Pro. We used an OEM Leupold DPP Pic mount here. (More details in the sidebar.)

For a weapon light, we have the SureFire XVL2. Visible light, visible laser, IR light, IR laser — it serves multiple roles in a tiny package, perfect for a PDW. 

As with our previous Flux Defense MP17 chassis, we used a Grey Ghost Precision slide with Griffin Armament barrel because they’re known variables when it comes to suppressed shooting. We note that the optic cover plate required a bit of a haircut to work with the Raider, but it’s nothing that affects operation — we could’ve easily just removed it, but we liked the aesthetic more with it installed. 

While early models of the P320 had a hard time properly shooting suppressed, there have been some in-line changes for more reliable operation. Will your slide/barrel combo work? Honestly, we can’t tell you until you head to the range yourself. 

Flux Defense MP17 Raider magazine well
The Raider magwell has almost entered ice-cream cone territory, but we haven’t encountered a baseplate it didn’t accommodate.

There are two QD slots on the Raider, one on the brace and one on the body. This is one of the only applications where we prefer a single-point to let this little semi-auto machine pistol hang.

For a silencer (because of course we have a silencer), we rolled with the modular, user serviceable Banish 45 from Silencer Central. While you can play around with configuration, we kept this one short for transport. See the sidebar for more information on this suppressor. 

And spray paint. Because it’s always spray paint. 


If you’re a lefty, take a pass on this one — at least for now. Or get some ambidextrous reps in. All controls and manipulations of the Raider are designed and intended to be used by right-handers. Some actions can be clumsily performed by a lefty, but it’s not an experience you’ll enjoy very much. We’re hoping to see a left or ambidextrous design with the next generation. 

The first Flux Defense MP17 model shipped with a holster, with Flux Defense eyeing law enforcement and military units as potential customers; Flux has yet to finish something similar for the Raider, but it’s an ongoing effort and may well be available by the time you read these words. 

Because the height over bore is so extreme with the Raider, before our first trip to the range we prepped with a laser bore sight. We didn’t run out of adjustment in either the shop or during live fire. 

We hit the range with confidence having had great experience with both the previous version of the Raider and our slide/barrel/silencer combination. And none of the above was a disappointment. Instead of breaking out our ballistic calculators and getting into high nerdery, we zeroed at 25 yards. It’s a bulked-up pistol with a plastic optic mount. And yet we were ringing steel at 100 yards with ease with a 12 o’clock hold.

Flux Defense MP17 Gen II Raider

Our decision to retain the manual safety was the wrong one. It’s nearly impossible to disengage with the firing hand. The folks at Flux told us we wouldn’t like it very much.  

The Raider is arguably more fun to shoot without a weapon light mounted. The utility of a light meant compromising our support a touch, but there are slots up front that a third-party is already making Picatinny adapters for. Those will be in our shopping cart soon enough. 


We fully admit that how much fun the Flux Defense MP17 Raider is makes up for the ergonomic issues of shoving a pistol into a carbine. This isn’t some giant plastic shell monstrosity though; it’s safe to think of the MP17 as making the P320 a more capable pistol rather than a full-on carbine conversion. That limited space means compromises inevitably have to be made. We could easily see the Flux Defense MP17 riding on an officer’s hip, as it’s not terribly larger than their service weapon, a sight damned smaller than an MP5, with much-increased capability. 

Now let’s see how she holds up. 

Flux Defense MP17 Raider Chassis

Weight (Naked): 18 ounces
Weight (Assembled): 40 ounces
MSRP: $459


  • GGP slide: $429
  • Griffin Armament barrel: $195
  • SIG Romeo2: $599
  • SureFire XVL2-IRC: $1,349
  • BANISH 45 silencer: $949

Price as configured: $3,980

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