Sig 9mm MPX Pistol PDW

The Sig MPX is an innovative configurable personal defense weapon (PDW) platform available in a variety of forms including pistol, pistol plus Sig Brace, rifle, and NFA-regulated SBR format. My choice is the Sig Sauer MPX pistol with folding Sig Brace adapter that you can easily purchase just like any handgun on the market and… it’s dead sexy.

Sig Sauer MPX 9mm pistol

To me, the Sig MPX is so freaking hot and sexy in a way that gets buyers all too excited to max out a credit card to own one. Yes please, take my money or I will continue licking your gun case. Just like that XX video tape your friend sold to you as a kid for two-months allowance in cash—you really didn’t care how much, or that your dad would kill you if he found it, you were on the verge of ecstasy to see what was on that tape. After the eighth or tenth time, that Dallas-based video about Debbie was hardly worth the money. Conversely, I would argue the $1600-plus street priced MPX is well worth the hefty price…and glaring stare from your significant other. The bonus to ownership is you get to don that grin—you know, ‘that’ grin—every single time you put it in your hands and squeeze the trigger.

Why a Sig MPX?

Of the guns many lust to have, the H&K MP5 is on that list. It is the timeless quintessential 9mm PDW that still serves in many militaries, law enforcement SWAT teams, and global hostage rescue teams for many reasons. It is utterly reliable, short, accurate, super easy to shoot fast, and hard hitting for a handgun round. In our minds, we all have a built-up mental image of perfection and want one. Then you get to fire an MP5 and it sadly resembles an accidental meeting years later of Debbie the porn star. The looks are still there, but the years of experience are showing with lots of wrinkles, bad skin, heavier than you thought, and indications of a serious high-cost substance abuse problem…sadly Debbie, the new models are much hotter. The H&K MP5 is kinda like that.

Despite its reputation, and my love affair with them, H&K has made some poor marketing decisions. H&K found itself in financial deep water and why they would not do consumer retro releases of some classic guns is beyond me. At a time when $400 Euro H&K P7 trade-in guns are going for $3000 on some sites, and shooters are still screaming for a civilian MP5. It seems H&K is leaving money on the table. Why has the semi-auto SP6K—updated MP5 semi-auto pistol—not made it to U.S. shores? Sig Sauer decided there was money to make in the MP5 market. Sig developed the MPX to go right after H&K’s throat with an adaptable, highly configurable, and openly supportable 9mm PDW format. Instead of a “me too” product, Sig also addressed all those gripes users had with the MP5 design. If you have always wanted an MP5, the Sig MPX will deliver more grins per dollar and I would argue is far better.

You Sexy Thing, Sig Sauer MPX

The MPX is arguably the sexiest and most titillating thing in decades to come out of Sig Sauer since the introduction of the MCX with the same profile only in 5.56 NATO. I mean, good lord, look at this thing—it is dripping with custom design concepts.

The design perfectly mimics the AR controls. And, Sig did not stop there. It added full ambidextrous controls on the magazine release, bolt charging handle, bolt release, and selector switch. Everything you can do with your left support hand, is possible with the right hand. Ambi selectors always annoyingly rub my trigger finger; Sig made the right-side selector toggle as short as possible, minimizing this known AR-15 ambi-selector issue. The charging handle stroke is a bit shorter than your AR-15 but it feels similar enough to use this platform for AR15 muscle memory reload drills. All around, all the controls are well-executed.

Sig Sauer MPX 9mm handgun

Sig made the MPX easy to customize. The new G2 version is fully KeyMod compatible with the plethora of aftermarket accessories. You can leave the rear picatinny spec rail bare, or with just one torque screw, you can use a folding or fixed adapter to mount an AR-15-compatible cheek stabilizing tube or Sig Pistol Brace. If you have your Form 1 NFA Tax stamp, you can add one of Sig’s fixed, folding, or collapsible stocks. The stabilizing brace adapters offered in fixed or folding models are fully AR-15 buffer tube-compatible, opening a world of possible accessories. Even the grip and trigger group are AR-15 compatible allowing you to swap out the unique grip and gritty trigger to something fitting shooter wants and needs. Flexibility is the base of this design.

The MPX is also a caliber-convertible platform offering users the option to swap out barrels and bolt systems from the factory 9mm NATO to .357SIG or .40 S&W—all just by removing two bolts. I would be shocked and stunned if at some point the public pressure was so great that Sig also offers this platform in .45ACP and 10mm. However, that is simply a hope at this point.

The heavily flared magazine well makes authoritative insertions fast and easily repeatable. It is a cannot miss reloading port that keeps the MPX happily rocking through 9mm after 9mm round. Honestly, the Sig Sauer MPX is hard to shoot without cracking a giant grin even if you must make due with shooting it as a pistol until your ATF SBR tax stamp comes in.

Even the magazines look freaking awesome. Lancer Systems—well known for its ultra-premium magazines—developed the magazine design for the MPX. Mag functioning is smooth and flawless. Reloading rounds is push-in AR-style versus slide in handgun mag-style which lessens thumb pain.

Yes. That Is It

When you buy an MPX, and you will, make sure you go ahead and get extra magazines. I now have six. Also, plan on buying 9mm ammo in 1000-round bulk packs. Otherwise, if you only take 50-100 rounds to that first range session you will feel like your hot significant other got you worked up and then left you high and dry.

Take all your magazines, along with 300-plus rounds, to the range. I can guarantee that you will not stop shooting until your thumbs are numb from reloading magazines. The high round count shooting experience will leave you satisfied in a way like that entire weekend you and your significant other spent in bed the first time you told each other you were in love. After several hundred rounds, you will be ready to sell all your other AR-15 pistols and SBRs and commit yourself to the MPX…not today or tomorrow, but ya’ know eventually because we are talking about guns here.

Shooting the MPX really doesn’t feel any different than shooting any other AR-15 pistol or registered SBR except that recoil is almost non-existent. Although a completely unfair comparison, by contrast my 9mm Keltec Sub2000 has a sharp little snap and the MPX does not. Sig did an excellent job with the piston-driven gas system, delivering a somewhat cleaner running gun and stripping out that jarring snap of the 9mm round hotly exiting the longer barrel.

Accuracy is freaking superb. Where the MP5 really shines is head shots under 75 yards, the MPX shines at this range as well. Hitting my action target hostage swinger—6 inches at 100 yards—was easy also. However, I did notice the 9mm round did not have the power to swing the hostage target to the other side. The gun is easily a single ragged hole gun at 25-yards; at 50-yards 3-4 inches for offhand groups were not difficult with quality defense ammo. Heck, with this accuracy, this could be a great little hunting gun.

This is a superb home and personal defense gun. With a 2 MOA red dot sight added, this was a freaky-fast little gun that delivered everything I love about .223 AR-15 pistols without the deafening report. You still need hearing protection with a 9mm handgun round going off with your cheek about 20 inches from the muzzle. With the MPX, earplugs are all you need for outdoor and most indoor shooting. The MPX has a slightly softer handgun report out of the 8-inch barrel. It is far from the ear-splitting boom an AR-15 pistol delivers indoors and out. With the right low penetration ammo such as Federal Guard Dog or the very hot IIIA defeating Liberty Civil Defense 2000-FPS 450-FPE, the MPX delivers accurate, high-energy dumping rounds combined with limited liability from pass-through rounds. For me, this gun is starting to make more sense for home and backpack carry personal defense than my AR-15 pistols.

For security work, I can see having a pistol with these capabilities in a very small 5.11 pack or messenger bag being a huge benefit in a mass shooter or hostage situation that requires precision shots. The question of whether the non-permanent Sig brace is or is not part of the total length of the pistol’s 26.35-inch length is a bit of a grey area considering whether this gun is concealable. It may be advisable to remove the extended Sig brace tube and use a standard pistol buffer tube to get the length under 26 inches if you intend to carry the Sig MPX pistol concealed in a pack.

MPX Annoyances

The price point and accompanying monetary outlay allows one to be critical of annoyances. The MPX is freaking expensive. I understand a ton of R&D went into this gun. However, that does not lessen the entry pain when it comes time pay. I remember still flinching hard even when buying it from Sig with my editorial discount— “Is that ‘with’ my discount?” I asked. The answer was yes, but the tightness in the front of my shorts still pushed the budget by adding four more magazines. At $1600 plus with only one mag is barely a third of the way to the price of a pre-ban select fire H&K MP5—and you can buy the pistol or Sig Brace model just like any semi-auto pistol without restriction.

The mag well is easy to find. Tactical reloads, where the bolt isn’t locked back, require a very firm whack to get them to seat with a full magazine. Although technically a piston-driven gas system, and cleaner running than straight blowback operation, this is still one dirty gun after a few hundred rounds. There really is no way around it—handgun rounds equal dirty guns.

For the price, I would have expected a Tritium insert on the front sight post and two magazines included. The polymer dust cover and finger stop both feel like they will break at any moment, but have not. The dust cover needs to be a bit beefier and I suspect one hard whack in a door jam and it’s a goner.

The magazines themselves are selling for $60-$70 which is painful even though they are stunningly well-made from Lancer. For me, the trigger is horrible, like… I am stunned Sig Sauer made it. How can Sig give me one of the smoothest double-action pistols on the market that has a trigger that feels like it had sand dumped into it. I am glad the trigger is compatible with an AR-15 compatible replacement.

The instructions leave something to be desired. The 10 pages of obvious safety warnings would serve users better if used to explain how to configure everything in the box. Speaking of everything in the box, there is an extra QD slung mount that took a good hour to understand how and where to attach it as I resisted the urge for an internet search.

Until you break in the folding stabilizing brace, which takes about 40 or 50 repetitions of feeling like you are going to snap the stabilizing brace off, you could swear that it locks both open and closed. I also found the stabilizing brace length to be about an inch too long to stabilize against the cheek. Some might find it the perfect length.

Final Thoughts

Functionally, the Sig Sauer MPX is a brick house of durability and a frontal assault on the MP5 moniker. The MPX had zero functional issues wasting away an afternoon with 1000 rounds of whatever was the cheapest 9mm ammo available in bulk. For those looking to have a 9mm AR-15 form factor in hopes of it “paying for itself in cheaper ammo,” the $1600 price tag makes that a bit unrealistic argument at current ammo prices.

Where I do see the MPX making sense is for personal defense weapon use. This little pistol can slip into most small packs or messenger bags and delivers a very fast response option with crisp precision. I recommend buying a 20-round magazine for this carry option as the 30-rounders are a bit long. The Sig Sauer MPX system screams for SBR stamping and that cool Sig collapsible stock. Designed for the person wanting a gateway to SBR registration—once you have your SBR Stamp, a stock swap is only one bolt away with the MPX. Buy the MPX like any other pistol, go and shoot it, send in the Form 1 NFA eForm to SBR the gun with a gun stock, and you can still go shoot the gun while you wait for that process to complete.

The Sig MPX is well-thought out, totally flexible, and configurable for future upgrades. This is an investment firearm that is more than just a toy fun gun. This is a serious piece of equipment perfect for home defense, as a mobile package for personal defense, and as a simple training tool also that anyone can use and train from with no worry of recoil. In today’s terroristic atmosphere, I may be carrying this in my pack more frequently. It delivers lots of firepower, has impressive accuracy, and it’s all in a nice reliable little package.


Caliber | 9mm NATO, Converts to .357SIG or .40S&W

Action Type | Select Fire or SBR (LE/GOVT ONLY)

Operating System | Closed, fully locked short stroke pushrod gas system

Overall Length (Telescoping Stock) | Closed Min 460 mm/18.1 in; Open Max 580 mm/22.8 in

Overall Length (Folding Stock) | Closed Min 425 mm/16.7 in; Open Max 610 mm/24.0 in

Overall Height (with 30 Rd Mag) | 265 mm/10.4 in

Overall Width | 52 mm/2.0 in

Barrel Length | 165 mm/6.5 in

Sight Radius | 270 mm/10.6 in

Cyclic Rate | 850 RPM

Features | Easily converts to 9 mm NATO, .357SIG, or .40S&W; user-configurable stock system – telescoping, folding or pistol configuration

What do you think about the Sig MPX 9mm? Have you shot one? Tell us what you think in the comment section.

9 Comments On This Article

  1. Was a good deal when they were about 1500. I waited 6months for one, when it came it went to 1850 with no sights…..told em to keep it.

  2. $1600 is a bit on the high side. My son was able to get one at a gun show for around $1200. He spent the rest on the stock and the magazines. I got the pleasure of firing it, and it will definitely put a grin on your face!

  3. I have the CZ Scorpion Evo 9 mm competing product
    $800 and 30 nround mags are $20
    The best part about it is that it is NOT AR 15 based
    I dont know about the rest of you, but I am bored with AR 15 type guns
    The Scorpion has the way cool “HK slap” where you can release the bolt to chamber a round by slapping down on the charging handle
    It runs forward with a very satisfying Kalunk!

  4. March14,2018 I just bought my Sig MPX .Happy birthday to me . I haven’t shot it yet, I do armed security and think it will be a great tool for the trade. Don’t know why people complain about the price. put a price on a life.