Flux Defense MP17 | Turn Your P320 Into a PDW [Review]

first published on December 2, 2019 by


Do you like unicorns? The MP17 from Flux Defense is the newest unicorn in the firearms industry. These things are incredibly hard to get your hands on, and we’re not entirely sure why. It may be because Flux Defense is a young company, and they’re experiencing some growing pains. It might also be that they’re simply selling way too much product to keep their shelves stocked.

Either way, we got our hands on an MP17 (we purchased a factory blemish from them because they’re right around the corner from us), and shot the hell out of it for you. Here’s our complete review of the system.

What’s the Purpose of a Stabilizing Brace.

MP17 Outside

A common misconception is that stabilizing braces are a gimmick, or specifically for disabled individuals. While it’s true that stabilizing braces do greatly increase the ability of disabled shooters, there is more to it. A stabilizing brace adds a third point of contact to the pistol, and allows the shooter a more stable shooting position.

With a stocked rifle, a third point of contact is made when the stock touches the shoulder of the weapon. This third point of contact enables the shooter to get proper bone support, and increase the lethality of the weapon. With a stabilizing brace on your pistol, you’re able to get a third point of contact with your forearm, which acts to further stabilize the weapon and increase it’s effectiveness. You’re also able to use it as a cheek rest, enabling the shooter to obtain a far greater and more stable sight picture.

If you have never shot with a stabilizing brace on a pistol, you really need to try it to believe. Once you do, you’ll never want to go back.

Meet the MP17 From Flux Defense.

If you’re unfamiliar with the MP17, then you’ve likely missed out on the viral video they released with the launch of their product. They have designed a system for the M17 and Sig P320 line of handguns that completely transforms the way the weapon works. Instead of just having a handgun on your hip, with this you essentially have a small personal defense weapon.

The operating group of your Sig pistol drops into the frame on the MP17 easily. In fact, the hardest part of the entire conversion was getting the mag release out of our Sig P320 X5. Once we conquered that small hurdle though, the rest of the conversion was smooth as silk, and we had the system running in about ten minutes.

If you want to know more about the system, check out this video from Student of the Gun where they cover down on the Glock variant.


  • Pic rail for pistol flashlights and IR Lights/Lasers
  • Optic mount works with most red dot sights.
  • Patent Pending one-handed deployment.
  • Optional Duty Holster
  • QD mount for slings.
  • Holds up to 43 rounds. Carries an extra mag.
  • Weight: 2.8Lbs (With full size slide – empty)
  • Size: (Collapsed) Height: 5.75” Length: 10.75” Width: 1.6”
  • Do You Need a Tax Stamp?

    Short answer, no. You do not need a tax stamp for the MP17 system.

    That’s not enough for some people though, so let’s address this fully. Flux Defense created the MP17 to be in compliance with all of the ATF’s regulations. The system, while transformative in nature, is only a pistol brace at the end of the day. That said, Flux Defense does make an SBR version of the system for those of you who are all about collecting tax stamps.

    Do they have an ATF letter? No. Free men don’t require permission slips, and this system is in compliance. If you want to read more about this, head over to our other Flux Defense review for the Glock System and give that section a read.

    MP17 on the Range.

    We outfitted our MP17 system with the Holosun HS507C red dot sight. The gun inside of the frame is the Sig P320 X5, which shoots like a dream straight out of the box anyways. When you combine the MP17 system, the Sig P320 X5, and the Holosun HS507C, something pretty amazing happens. Your ability to stretch the firearm’s capabilities increase exponentially. You turn the handgun into a monster PDW.

    I consider myself a slightly above average pistol shooter, let’s get that straight. I’ve never competed in anything outside of trying to get range high on the M9 qualification course for the Marine Corps. With this system, I was able to consistently and quickly ring steel targets from 25 to 100 yards. If I stretch a regular handgun to 100 yards, I will ring steel maybe once every 6-8 shots, and these shots will take a considerable amount of time.

    The third point of contact from the stabilizing brace combined with the parallax free red dot optic from Holosun truly made me a far better shooter than I normally am. If that’s something you think you need, then we suggest finding one of these systems and giving it a shot. You’ll be amazed at what these tools are capable of helping you achieve.

    Practical Uses of the MP17.

    Flux Defense Bench

    For some reason, we’ve noticed that people seem to not understand the purpose or mission of the MP17. Aside from the obvious comments from confused individuals asking if the MP17 requires a tax stamp, there seems to be a number of people who simply “don’t get it.” They don’t understand who needs an MP17, and they don’t understand why it even exists.

    Aside from the third point of contact from the brace, there’s a long list of people who need one of these. Let’s go over a few of those people, and explain why this works for them. Hopefully we can answer some of those questions.

    School Resource Officers.

    Depending on where you are in the country, your local school resource officer may or may not have access to a rifle. This happens for a number of reasons, chief among them being that they SRO is simply not allowed to have a rifle on school grounds. While the department may be able to give the officer access to a patrol rifle, the school straight up doesn’t want it inside of the building.

    If your patrol rifle is off school grounds, or in the trunk of your car, it may as well be on the moon. Fights happen fast. When an SRO needs to react to a threat inside of the school, they probably don’t have the time to get outside. The Flux Defense system is a solid alternative for School Resource Officers that puts them on level ground with an untrained active shooter with a rifle.

    Military Pilots.

    This should be a no-brainer. Cockpits are notoriously tight spaces. So tight in-fact, that often pilots are forced to find creative ways to carry their expensive PDW that still allow them the ability to access all of their in-flight controls.

    Due to it’s collapsible nature, and compatibility with the military’s newest service pistol, the MP17 should be a go-to choice. Only time will tell if the military decides to adopt this system, or go with another PDW which has a much higher cost attached to it. We hope they see the light.

    Close Protection Agents.

    MP17 On Workbench

    The more concealable a close protection agent’s weapon, the better. These guys and gals are escorting some of the world’s top people. Often, these people are in situations where their close protection agent needs to go unnoticed. A PDW system that is compact and lightweight gives the agent the ability to blend in, while not removing their ability to react to a threat.

    Without a shadow of doubt, the MP17 is a near perfect system for these people. They can fit inside and out of vehicles with ease, and carry an ultra concealable weapon system at all times. While they are still limited by the Sig P320 or MP17’s maximum capabilities, this tool allows them to stretch those capabilities to the individual operator’s maximum potential.

    Anyone Looking For Their Next Truck Gun.

    Last, but certainly not least, the MP17 is perfect for you. Since this system is a brace, it requires no extra permission slips from the ATF. The average person may not always need a tool like this, but it’s always better to have and not need.

    Coming in at right around $450, you’ll get all the capabilities of a PDW, at a fraction of the price. If you’ve been looking for a new truck or bug-in-bag firearm, you’ve found it here.

    Final Thoughts on the MP17 from Flux Defense.

    MP17 Side View

    I’m going to be straight with you. The MP17 is my new favorite platform for shooting. The Sig P320 X5 that we have installed it on is also a champ. Getting this thing out on the range and rocking it has been an adventure every single time, and I don’t think that’s going to change anytime soon.

    We’re working with Flux Defense to test their safety system, and so far have had no major issues. Using a brand new system like this is awesome because it allows us the ability to innovate techniques. In practice, this weapon system has been impressive at every single turn. We look forward to seeing what we can get this system to do every time we’re on the range with it.

    We know these things aren’t easy to get though. Let us know down in the comments what you think of the system so far. Have you had the opportunity to get your hands on it yet? Are you interested in purchasing one when they get a a little easier to obtain? We want to hear from you down below.