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For the past several decades, a handful of companies have dominated the submachine gun field, and this short list certainly includes H&K and their popular MP5 line. Known the world over for its reliability and accuracy, just about every agency armed itself with those rock-solid firearms, and the model has become a classic.

But even though MP5s continue to be picked up by some agencies—even on a second-hand basis—and frequently trade hands between enthusiasts, the model line doesn’t have all the modern amenities we’ve become used to, especially all the rail space we need for optics, lasers, lights, and so forth. Additionally, more advanced operating systems have been developed to work reliably with various types of modern ammunition, and lighter materials have been employed to carry weight.

Recently, SIG Sauer has stepped in to help fill some of the submachine gun void with their new MPX line of products, and it seems to have struck a chord with the public and with myself as well. The first time I pulled the MPX-P out of the box, it felt good in the hand, and it looked good as well. It’s quite apparent the latest technological innovations have been used to put together this masterpiece of engineering, and it looks like it had more than one or two industrial designers to make such a beautiful weapon.


Construction Details

The SIG MPX-P is the civilian version of their new line of MPX short-barrelled and fully automatic weapons. Because of the current rules set forth by our government, civilians can’t put a stock on something with less than a 16-inch barrel, unless they pay an exorbitant tax to the BATFE for the ability to exercise what should be a fundamental right to begin with.


The rear sight is adjustable for windage, and offers different aperture sizes to adjust the precision of the shots. The charging handle is the same type found on AR-style weapons, making this part of the system familiar. Additionally, there’s a mounting spot on the back to attach a stock if one were to legally convert this to a short-barrelled rifle.

The same goes for fully automatic weapons. You must pay for the privilege of exercising your right with those types of weapons as well. To me, it’s the Second Amendment equivalent of a poll tax. The build quality and finish of the MPX-P is fantastic. It’s solidly constructed, has an ergonomic design, and was 100% reliable during the time I had it for review. The operating system is a closed, fully locked short stroke gas-piston mechanism, which is an additional safety measure for the user. The pistol is semi-automatic only for the general public. The forend is an aluminum rail with a rail-adaptable handguard that’s comfortable to hold, while still offering plenty of options to add accessories by adding two-inch Picatinny rails to the forend. The MPX-P came with three two-inch Picatinny rails in the box. Several controls are similar to AR-style platforms, including the safety selector, bolt release and magazine release, all of which are ambidextrous. Additionally, the MPX-P sports a charging handle similar to those found on AR-type firearms, and it has a monolithic receiver with an integrated M1913 rail (Picatinny) in the 12 o’clock position.


The MPX-P has familiar, AR-style controls as well as a few ergonomic touches such as the handle with the palm swell and the lower trigger guard being offset for use by gloved hands.

Lacking the stock found on similar models, the weight is only five pounds with an empty magazine. Speaking of which, the magazines are made by Lancer Systems, come with steel lips, and are available in 10, 20 or 30-round capacities. The overall length of the MPX-P is 16.85 inches with a barrel length of 8 inches. An additional bonus is that the MPX submachine guns are built to allow the user to change the barrel length and stock type in the field. Also in the package from SIG was a semi-flexible single-point sling with a push-button QD attachment to insert at the rear end of the pistol. And, there was one magazine in the box. To their credit SIG includes a coupon that allows the purchaser to buy a few more mags at once to save some money, but for a high-end weapon like this, I honestly believe two magazines should be the minimum sent out from the factory.



For what it is—a very large and heavy semi-automatic pistol—it handles pretty well. I liked the feel of the rounded grip as opposed to some of the standard AR grips, and the comfortable, rail-adaptable handguards that make handling the forend more comfortable than a typical quad rail. It also has a hand stop at the end of the rail to help prevent the user from getting their hand around the end of the barrel. The MPX-P has flip-up iron sights that are nicely built, and different aperture sizes are available on the rear sight for more precise shot placement. However, a weapon of this type begs to have some sort of optic on it, so I chose to install the Lucid M7 Micro Dot sight to make acquiring the target easier, and to more accurately assess the pistol’s accuracy.


Even though the MPX-P comes with nice flip-up iron sights, the 12 o’clock rail is considered a must-have on today’s combat weapons for the addition of optics for faster target acquisition.

Now, I believe that the MPX-P is missing a couple of things that would make it a truly effective and practical weapon. Since there is no stock, it’s tough to get a stable sight picture. Without it, the user is awkwardly holding five pounds of weaponry with two hands, while trying to both stabilize the pistol and get a good sight picture at the same time. Though the single-point stabilizing sling helps a good deal, it’s still not an optimal set-up for firing accurately.

Also, the eight-inch barrel doesn’t really add a lot over a standard pistol barrel. From the research I’ve done, you don’t really get the majority of peak velocity unless you’re at 12 to 14 inches of barrel length. There are exceptions, of course, but I’m just speaking as a general rule of thumb. If this was a fully automatic pistol, that’s a little different; with a rate of fire of 850 rounds per minute, you could dump 14 rounds into a target in one second. But, we knew all these things going into the review, so the shooting evaluation is based on what it is, and not what it could be.


MPX-P On the Line

Right off the bat, the trigger pull felt gritty and heavy. After the second magazine was finished, the grittiness started to go away and things started smoothing out for us. After 300 rounds were sent downrange, the trigger pull was still a stout 7 pounds at the midpoint of the trigger. I would assume the heavier trigger is a consequence of the original MPX being a submachine gun, and you wouldn’t want a hair-trigger on one of those. The first 120 rounds were used to break-in the MPX-P and to plink around a bit. I hadn’t used HPR Ammunition before, but they supplied the bulk of the ammo for this review, and I was pleasantly surprised by the results. The 115-grain 9mm JHP loads were clean shooting, and were in the same field with the premium, higher-priced ammunition when it came to accuracy. At $30 for a 50-round box, it’s hard to beat.

Speaking of accuracy, I tested the MPX-P with several high-end rounds including 124-grain Federal Hydra-Shok, 115-grain Hornady FTX Critical Defense, Federal 115-grain JHP +P+ (9PBLE), Black Hills 124-grain JHP +P, and the HPR 124-grain JHP loads. For the accuracy testing, I shot from the bench at 25 yards with the Lucid M7 Micro Dot attached, which made it much easier for me to ensure I was keeping the same hold between shots.

As with the opening session of break-in shooting, all of the various brands and loads fed perfectly, with approximately 350 rounds fired in total. Running five-shot groups during the testing, the average group size was 3.04 inches, and the best group of the day was brought home by the Federal 115-grain +P+ JHP at a 1.25-inch spread, with the HPR 115-grain JHP following closely in second with a spread of 1.375 inches.

In fact, almost all the loads got close to those numbers at one time or another with the large number of groups fired, though those groups weren’t the norm. Using the Lucid M7 Micro Dot helped immensely, but I can still only see so well at 25 yards without magnification. And, while I understand the MPX line is made for combat, the heavy trigger pull didn’t help in terms of getting tight groups.


The MPX Lets its Hair Down

I still had a decent amount of HPR ammunition left over, so I took the MPX off the bench, attached the single-point sling, and went to work offhand on a Thompson Target B34 STOP target. Still at 25 yards, I pushed the pistol out until I met resistance from the sling. That helped stabilize things, and I shot 20 more rounds—5 in the head and 15 in the chest. With the benefit of the M7 sight, I had a fairly easy time staying on target and getting some pretty decent shots. I didn’t get target-match groups, but all of the rounds hit critical areas, and any one or two of them would have put the threat down.


There came a moment to have some fun, and by utilizing the sling as a stabilizer and with the aid of the Lucid M7, twenty rounds of the HPR 115-grain JHPs all found their way to the critical zones of the B34 Thompson STOP target—from 25 yards.

Velocity Data

With the eight-inch barrel involved with the shooting exercise, it’s only right to wonder how much of a bump the 9mm gets with the extra barrel length. It wasn’t a very dramatic increase, which was what I believed at the beginning of the exercise. Here are the average results of different loads’ velocity at 10 feet:

Federal 124 Gr. Hydra-Shok 1192 feet per second
Hornady 115 Gr. Critical Defense 1234 feet per second
HPR 124 Gr. JHP 1107 feet per second
Black Hills 124 Gr. JHP +P 1298 feet per second
Federal 115 Gr. JHP +P+ (9PBLE) 1397 feet per second

It seems to me that a barrel at least 12 inches long is needed to pull the most velocity out of the various 9mm loads on the market. Without the advantage of full-auto fire, the eight-inch barrel provides only a slight enhancement of speed versus a four-inch barrel.


Final Thoughts

So, what’s the verdict? I have to say that I’m a little conflicted. Because of the superb build quality, great ergonomics, utter reliability, and the familiarity of AR-style controls, I really want one. With regard to design and functionality, this is one of the better pieces to come along in a while. Even the magazines look solid and precisely built.


The 33-round magazine is made by Lancer Systems. It feels very solid and has metal feed lips that will last longer and not spread apart.

But, from a purely practical standpoint, and thinking like a survivalist (or prepper, if you prefer that term), I have to ask myself what role this particular pistol would play as part of my overall plan. I have pistols that come with 33-round magazines and make a much more portable and concealable package. I don’t lose much with optics, because there of plenty of adapters or gunsmiths available to fit a red-dot sight on a semi-automatic pistol, and the velocity from an eight-inch barrel isn’t tremendously better than from a four-inch barrel.


The stabilizing sling and the Lucid M7 Micro Dot made a great combination for acquiring the target and staying on it. Utilizing the hand-stop to keep resistance on the sling helped reduce fatigue since the user doesn’t have to constantly keep a tight grip on the forend.

However, as it sits, the MPX-P is bursting with potential. If one were to take the time to deal with the BATFE, pay the expense to add a folding stock and make it a short-barrelled rifle, this would be an excellent low-recoil weapon to move around the house with to defend your family, or keep in your vehicle in case everything goes sideways. It would even make a fairly light weapon to keep with you when you need to conserve weight as you’re bugging out on the trail.

So, really, the decision is up to you. Are you a totally practical person, or do you like to treat yourself from time to time? If you accept the fact that, right now, it’s a bulky, five-pound pistol with excellent design features and superb functionality, then you won’t be disappointed in the least. In fact, you’ll love everything about it. GW



Manufacturer/Model: SIG Sauer MPX-P

Caliber:               9mm

Action:                Semi-automatic

Rails:                   Aluminum, mono

System:              Closed, fully locked short-stroke, gas piston

Weight:              5.0 pounds

Length:               16.85 inches

Twist:                  1 in 10 rifling

Barrel:                 8 inches

Trigger Pull:      7.6 pounds

Capacity:            10/20/30 round magazine

MSRP:                $1,576



Lucid M7 Micro Dot

Cast Aluminum Frame

Built-In Rail Mount

Weight: 4.6oz

Waterproof & Fog proof

100% Shockproof (.458 SOCOM)

Reticle: 2MOA Dot 25MOA circle

Auto Brightness Sensor

Auto Shut-Off (2 hours)

7 Brightness Levels

Battery: 1, AAA (Not Included)

1/2 MOA Adjustments

Parallax Free

21mm Objective Lens

1x Unlimited Eye Relief

Limited Lifetime Warranty

MSRP: $229


Editor’s Note: A version of this article first appeared in the January 2016 print issue of Gun World Magazine.