MP17 Review – Flux Defense MP17 PDW for Sig p320 [2020]


In this Flux Defense MP17 review, we’re going to cover what the MP17 is (and what it isn’t). First, the Flux Defense MP17 is NOT a firearm and the sample we tested isn’t a rifle either. It is, however, a really novel concept on the PDW platform.

We’ll give you a hint about what we think about the MP17: We LOVE it. But, it had to grow on us first. Read on to see what we mean.


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Reliability: A+
Accuracy: A
Shootability: A
Ergonomics: B
Value: A+

Final Grade: A+

Flux Defense MP17 Background

PDWs are very popular now. It seems like the industry is flooded with 9mm carbines. And why not? They’re a ton of fun to shoot, low recoil, compact/concealable, and they shoot inexpensive ammo.

Also, the PDW (Personal Defense Weapon) style is popular with executive protection teams.

However, most 9mm carbines/PDWs are dedicated platforms that don’t share anything in common with a sidearm. The problem with this is, especially in a tactical scenario, lack of commonality of parts and magazines. If a soldier or officer has a 9mm PDW, there’s a good chance that they have to carry two different types of magazines for their PDW and sidearm. Also, parts between the two are not interchangeable.

Flux Defense solved these problems and more. By making a platform for a firearm (and not a firearm itself), the MP17 can take the guts of a Sig p320 and it uses p320 magazines. This means that most parts between a completed MP17 and Sig 320 are interchangeable and the magazines can be used in both!

It’s a really novel idea by Flux Defense. But, does it work?

MP17 Specs

Host PlatformSig p320
MagazinesP320 Mags
Weight2.8 lbs
Length (collapsed)10.75″
Capacity38 rounds

Flux MP17 Features 

1. Light and Compact PDW-style Chassis
Makes the MP17 quite possibly the best PDW platform.

2. Extra Magazine Storage
Allows 38 round capacity on-board with factory mags.

3. Spring Loaded Arm Brace
Collapses for a small footprint and deploys quickly with one finger.

4. Optics Ready
Mounting options for all major red-dots and even a picatinny rail.

Flux Defense MP17 Review – Our Take

The Flux Defense crew sent us an MP17 (pistol brace version) for us to review.

Full disclosure: My first thought upon seeing the MP17 online was…. “huh?”

I couldn’t understand why someone would put all of that…stuff… onto a Sig P320. Once I realized that it wasn’t adding things to a p320 but rather it was its own thing, that is the smallest and lightest 9mm carbine-style platform available that used readily available parts and magazines, with some p320 parts inside, I saw its genius.

Seriously. It may not look like what you expect to see but it is AWESOME.


Here’s how I look at this novel platform (seriously Flux Defense crew, kudos on thinking outside the box and taking advantage of the p320 modularity): If you’re looking for a 9mm carbine-style firearm, you probably want it to be small and light. You also probably don’t want to purchase expensive proprietary magazines (or an expensive firearm for that matter). Also, you might be concerned about the reliability of the platform.

Well, with the Flux Defense MP17, you get the lightest, smallest, and least expensive PDW (9mm carbine style firearm) that uses the same operating components as the pistol selected by all branches of the military for its reliability and it uses the same magazines that are readily available (and that may also work in your sidearm).



Before I took the MP17 to the range, installed a p320 mag release, the chassis from my x-compact, and a full-length p320 slide. The chassis was a bit tough to get in the first few times I tried. I think this is due to a tight fit in the plastic housing and learning to get the slide releases easily between the MP17’s support bars.

I then took an RMR off of one of my pistols and went to install it on the MP17 and started to curse the Flux Defense crew. The flat top of the MP17 meant that my RMR mounting screws were too short. I mumbled to myself that they should have included the right length screws for their special platform and right as I moved the box it came in…. you guessed it… I found the screws they included for all the major red-dot platforms. Oops. Maybe I should read the instructions and check all the parts before I get frustrated. ­čÖé

I took the Mp17 out to the range to put it through its paces and I’ve taken it a few more times since because it is so fun to shoot.

What I Liked:

MP17 Sig p320The MP17 is the smallest, lightest, and least expensive system in its class. For example, CZ Scorpions, Sig MPXs, and AR-style 9mm platforms are larger, heavier, and more expensive than the MP17.  Check out my short video above to see how tiny the MP17 is and how it fits in the tiny back pocket of my bag.

The MP17 is super fun to shoot. It isn’t just a great platform for me, it’s easy and fun for smaller-framed shooters like women and children too.

There’s tons of firepower (almost 40 rounds with factory magazines on-board) with magazines from your pistol (if you shoot a p320) as backups.

Flux MP17I can’t get over how great it is that I can use the same spare parts and magazines for my MP17 as I can my p320. I know that the Army recently selected the B&T 9mm PDW, in part because it took p320 magazines. I really wish the Army took the MP17 instead – the military is all about supply chain and uniformity. This would make it easier for logistics and soldiers! And, it comes with a holster (see below)!

The MP17 made me more accurate and allowed me to shoot faster than I can with just a standard p320. But, not by much. I’ve been practicing handgun a lot lately and I’s say it gives me a 10% speed increase for any particular drill. However, even though it isn’t a major change, the confidence and accuracy in my shots makes me that much better. Also, as I’ll touch on below, it made a bigger difference for less experienced shooters.

Although it’s not a rifle, I could still shoot the MP17 further than I can reliably shoot with just a handgun. Just for fun we were repeatedly smacking a silhouette at 200 yards.

You can tell that the Flux Defense crew really though this thing through – they even have a window in the housing that allows a shooter to use the slide’s iron sights if needed.

Also, the spring-loaded arm brace is not only fast to deploy, it’s a lot of fun too (don’t judge me).

What I didn’t Like:

I wish the MP17 came with a p320 mag release installed. This is the only part that keeps the MP17 from being an easy swap from pistol to PDW. Well, it’s still fairly easy, but it’s not as simple as it could be if it came with this small part.

Flux MP 17I’m fairly tall (and have a big head) so the pistol brace is a bit on the short side for me to shoulder (my face is closer than I’d like but this isn’t a rifle, it’s a super compact PDW).

I really like to use a slide release (yes, I call it a slide release… you can “correct me” in the comments below) and the MP17 is designed in such a way that it doesn’t allow access to the p320 slide release. This isn’t poor design, I think it is just not feasible.

The one thing I asked them to improve was the spare mag holder. They already mentioned that they’ve improved it and that I have an earlier model/prototype. The spare mag holds in place with friction and can be very difficult to remove. Ideally, I’d like to see another p320 mag release included but mounted on the other side (might as well take advantage of the ambidextrous features) ┬áso it’s not so easy to accidentally engage.

MP17 320 Sig


So, how small is it? When the brace is collapsed, the MP17 fits into my favorite pistol safe, the Fort Knox PB1. That makes this about 100 times better for home defense than just a handgun!

If you’re looking for a 9mm carbine-like platform, and especially if you already have a p320, you’ve got to give the Flux Defense MP17 a look. It’s lighter, smaller, and less expensive than anything else and it ran with flawless reliability for me and it uses commonly found parts and mags.

What’s not to love?

Now, be honest, did I change your opinion at all? Let me know in the comments.

Although the MP17 can be used with any small-frame (9mm, 357 sig, or 40 S&W) slide, any slide shorter than full length should be used with a compensator for safety.

Flux Defense MP17 Pros and Cons

Super light

Super small

Reliable and fun

p320 parts commonality

true innovation (nice to see in the firearms industry)

Doesn’t include mag release

A bit short (but, it’s supposed to be)

Can’t access slide release

Awkward spare mag storage

Report card

ReliabilityFlawless reliability (appx 1,500 rounds of Magtech 9mm shot so far)


AccuracyPeak accuracy from a p320 platform. It’s not a rifle, but it lets you stretch out farther and more accurate shots than you could likely do with a pistol alone.


ShootabilityThe MP17 made me a bit faster and more accurate than a p320 alone. However, when I gave it to some fairly novice shooters, their abilities improved a LOT with the MP17


ErgonomicsI love how they designed the MP17 – it is very intuitive to hold and use. However, it’s a bit too short for me, the housing pushes my firing hand lower than I’d like, the spare mag holder isn’t ideal, and I wish the slide release was accessible.


ValueFor the money, the MP17 can’t be beat. Even if it cost more, I still think it’d be a great value for what it is… the simplest, smallest, and lightest PDW.


Final Grade: A+

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MP17 vs Other 9mm PDWs (MP-5, AR 9mm, Scorpion, Sig MPX)

  • As you can see in the table below, the MP17 beats the others in dimensions, weight, and cost. Add to it the commonality of parts, and you’ll see why I’m so crazy about something that looked so weird to me at first.

MP17 Holster

Holster MP17The Flux Defense MP17 has an equally thoughtful/novel hoslter available for it.

The MP17 holster accepts any Safariland holster mount (again, great job with the commonly available accessories guys…. I wish more manufactuers thought this way) and allows the MP17 to be holstered with an optic, with a light, and… get this… even with a silencer!

The retention holster releases the MP17 with a thumb push-button and works very well. However, it is very awkward to walk around with if you’re trying to compare it to a regular handgun holster. However, when compared to any other 9mm carbine-style platform, it is WAY easier to transport and carry.

That’s the common theme, I think, with the MP17. If compared to a normal handgun, it’s awkward. When compared to any other PDW-style firearm, it’s beautiful!


Flux Defense MP17 Upgrades and Accessories

If you already have an MP17, or if one is on its way to you, then you’re going to want a few extra items.

First, you’re probably going to want more Sig P320 magazines and 9mm ammunition for your MP17 becuase it’s going to be so much fun, you’re going to shoot a lot!

Here are our choices for magazines and ammunition for your Flux Defense MP17 (assuming you have a 9mm p320). Please note that you are going to need full-size magazines for your MP17 and we like having the extended magazine in the pistol grip and a standard full-size magaine in the magazine holder in the front – this keeps the base of both magazines at the same level.

p320 Magazine

21 Rd 9mm Extended

p320 magazine extended

p320 Magazine

Full-size Standard

Magtech Ammo

9mm Ammunition

magtech 9mm

Optics For Flux Defense MP17

Although you can use the p320 slide’s iron sights to aim, a red dot sight makes it much easier!

You can use a slide-mount-style red dot or a bigger red dot meant for mounting to a picatinny rail. We like the lower profile slide-mounted style for the MP17 but a bigger red dot could be handy too (although not as compact).

For slide-mount styles, we really like the Tirijicon RMR sights for their durability. You can get an electronic true red-dot RMR or you can get a dual illuminated RMR which works with tritium and fiber optics (this is what is on our Flux MP17).

Here are our favorite optics for the MP17.

Trijicon RMR



Trijicon RMR

Dual Illuminated

dual illuminated RMR

Sparc II

Red Dot

sparc ii


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  • Ryan Cleckner
    Posted December 31, 2019 2:55 pm


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    Posted December 31, 2019 3:26 pm


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    Posted January 12, 2020 11:30 am


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