Black Rifles & Tactical Guns

Gun Test: SIG’s MPX 9mm Pistol

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By Will Dabbs MD, American Handgunner
Photos By Sarah Dabbs

I worked for a solid year as a janitor to buy my first AR-15 when I was in the Tenth Grade. I first coveted, then schemed, then slaved until I made it mine. That sexy black rifle was, at the time, my most prized possession.

Habituation is the doctor word for my problem. Nowadays I get my mitts on cool black iron with some frequency and I do so love pawing over something new and oily. However, I have become a bit jaded. After more than two decades writing for gun magazines I figured I had seen everything. Then I met the new SIG MPX.

Simply put, the MPX 9mm pistol pegs the Awesometer. I thought it impossible to impress me with a cool new gun. It turns out I was wrong.


It’s kind of hard to believe this gun is simply a handgun in the eyes of
the government. When nicely accessorized the SIG MPX pistol is still
handier than your average M4 and would make an ultimate home-defense setup.

Vital Statistics

The SIG MPX is technically a short-barreled, gas-operated 9mm handgun. The receivers are aluminum and the gun fires from the locked breach via a short-stroke gas piston system not unlike that of the M1 Carbine. The charging handle is a miniaturized version of that found on your AR-15. The manual of arms is the same as that of every M4 you have ever hefted.

The gun feeds from 10-, 20- or 30-round polymer translucent curved magazines incorporating steel feed lips. These magnificent Lancer-made mags are, however, just a bit too large to fit into MP5 pouches. The KeyMod rails accept all the standard stuff and the gun weighs a paltry 6.5 pounds. The basic chassis will eventually be readily convertible between 9mm, .357 Sig and .40 S&W. Trigger pull is a bit north of 7 pounds and feels about like that of a rack-grade AR. The gun includes a single-point sling and incorporates a polymer pop open dust cover over the ejection port. Literally everything is ambidextrous. Imagine the nicest high end tricked out black rifle you’ve ever held. Now picture it recoilless and custom-designed around the 9mm cartridge and you’ll have the MPX.

Okay. Interesting, I’ll grant you. But I suspect most of you have not yet been knocked sockless. The game changer for the SIG MPX is on the tail end.

SIG’s truly revolutionary Pistol Stabilizing Brace defined an entirely new genre of firearms in the United States. Designed by a Physical Therapist to allow amputees returning from the ongoing kinetic festivities in the Middle East to run a proper gun one-handed, these delightful devices strap to the shooter’s forearm and provide greater stability than might otherwise be the case. The beauty of the device is that BATF has certified on numerous occasions that installation of the PSB does not change the classification of the weapon as a pistol. This means the barrel can still stay short. In the case of the MPX, they actually mounted the stabilizing brace on a strut that folds to the left side of the gun when not in use.

The new SIG MPX just screams submachine gun — yet doesn’t require a transfer tax. And remember, it’s semi-auto. BATF has been fairly schizophrenic in their opinions regarding whether it is legal to bring the thing up to your shoulder. I’ll let you figure that part out for yourself. As Jessica Rabbit said, “I’m not bad, I was just drawn this way.”

However, I think the PSB-equipped MPX may be the neatest new gun I have ever seen. And it does keep the door open, too, for disabled handgunners to keep shooting one-handed.


The pistol stabilizing brace on the SIG MPX folds to the left when not in use.


The key to the extraordinary amount of pure unfiltered awesome packed into the
MPX is the revolutionary pistol stabilizing brace. This inspired device was
designed by a physical therapist to help combat amputee veterans shoot again
and results in an entirely new breed of firearm.

Running The Gun

Recoil is a joke. It doesn’t exist. The overall impression is a bit like having shrunk your favorite AR down to something that would fit into a briefcase. Mount up a proper light/laser module like the SureFire X400 and top it off with a SIG red-dot sight (SIG makes those, too, by the way) and you have a whole vat full of awesome. PeeWee Herman could tote one of these things around for a week and then start donating excess testosterone to those less fortunate.

Double taps flow forth like music and the gun will reliably bring the rain on a man-sized silhouette out beyond 100 meters. In fact, popping steel a football field away with a 9mm ball will reliably cure what ails you. Additionally, you can spend an afternoon at the range without feeling like you have to sell a kidney to cover the ammo.

The SIG MPX maneuvers indoors like an MP5 but magazine changes are faster. The gun runs nicely both right-and left-handed; and it takes corners like a Bugatti. Ball rounds of various weights, cheap steel-cased blasting ammo, bulk pack, and high tech defensive hollow points run through the MPX like grain through an incontinent goose.

The barrel is threaded to European SIG standard left hand 13.5 x 1 metric threads. This means American 9mm suppressors won’t fit without an adaptor. I found one easily enough online and mounted up my trusty Gemtech GM9 G-Core can. The GM9 is a monocore design cut from a solid cylinder of 7075 aluminum. It comes with a built-in LID device for reliable operation on a handgun but perches just fine on the end of the gas-operated MPX as well.

As the muzzle sports left-hand threads and the can uses right-hand threads, take care to keep everything tight. I mounted up the suppressor adaptor with a bit of thread-locking compound just to be sure. Be forewarned, however. Slap a .22-caliber AR flash suppressor on that 9mm muzzle and you just converted your nifty new SIG MPX into a bomb.


With a red-dot sight, a SureFire X400 light/laser module, and a top-notch Gemtech
GM9 G-Core suppressor the SIG MPX is arguably the coolest piece of tactical iron
available at any price.


Will thinks the new SIG MPX is the “coolest”new gun on the American market in a
generation. Fast, agile, and awesome, this remarkable firearm transfers without
any more hassle than a standard handgun.

What’s It Good For?

I defy you to contrive a better home defense solution than the MPX without investing in an NFA tax stamp. The gun folds up small enough to ride high on a closet shelf or tuck behind the bed so long as there are no little fingers that could get into it. The gun would fit behind the seat of your pickup truck or ride over your shoulder painlessly during a stroll through the sorts of places where the Wild Things Are.

A SIG MPX along with half a dozen magazines packed with expensive social ammo during a hurricane evacuation, disruption of social order, or zombie invasion is like vaccinating against criminal opportunists. Only the most oblivious ne’er-do-well would fail to look for easier pickings elsewhere if confronted by a determined survivor toting SIG’s latest compact tactical beastie.

There are lots cheaper, lighter ways to throw 30 9mm bullets downrange. However, there is literally no more effective way to do it at any price. Additionally, the MPX looks cool beyond the capacity of the language adequately to describe. Robust, reliable, accurate, reasonably priced for its niche, and badder than anything else in your collection, the SIG MPX represents an entirely new species of firearm.

If it sounds like I’m impressed, I am. I’d say they did good.

Thanks to American Handgunner for this post. Click here to visit

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