SIG-Sauer MPX Pistol, by Pat Cascio

This 9mm pistol, and it is a pistol, has been discontinued by SIG-Sauer for some reason…and they now have a shorter, smaller version called the Copperhead. I received an early version of the MPX for testing, and I’m just now getting around to finishing the article I started a few years back.

Right now, there is a lot of confusion, caused by politics and the BATFE, over certain firearms. Until recently, the ATF has held that pistols, with an arm brace or wrist brace, is legal to own and use. But the BATFE, as always, just keeps changing the rules on this matter. Some many years ago, the BATFE said that you could have an arm or wrist brace on these types of pistols. Then they said that you could NOT shoulder the gun when you fired it, or that would be a “de-design,” Then, the BATFE said that, you could shoulder the gun – intermittently. Most recently, they proposed a totally arbitrary set of “standards” for evaluating arm-braced pistols, with a felony for the owner of any braced pistol that goes over a certain number of “Points.” This has been one big confusing and contradictory mess!

Politics have entered this debate, and with the new Administration in the White House, and they are very anti-gun, they are pushing the BATFE, through Executive Orders, to reclassify these pistols the same way you’d treat an NFA weapon – and that means you will have to register them as a “Short-Barreled Rifle”, with fingerprints, the consent of your local Police Chief or Sheriff, and a $200 transfer Transfer Stamp.  Or, you might have to turn them in so they can be destroyed, or you might turn the pistol into a rifle, by adding a 16+” barrel or by welding on a really long flash hider or barrel extension to bring it to 16+ inches. It’s a vicious circle, but in the end, I believe the FedGov will outlaw these pistols – with or without an arm or wrist brace.

Make no mistake, the new Administration is totally anti-gun – everyone Biden appointed to various Cabinet posts, are anti-gun. So, it will be a constant uphill battle when it comes to owning guns – any type of guns. And, needless to say, they want to ban all magazines that hold more than 10-rounds of ammunition – and that, I’m sure is only the start of many restrictions to come our way.

Anyone who is the least bit familiar with SIG-Sauer firearms, knows they produce some of the most reliable firearms on the planet, and they are always coming up with new designs, and that is why I believe the original MPX was discontinued to make way for the smaller Copperhead version.

A little bit about the MPX is in order. As mentioned, it is a pistol, no matter what some politicians might claim – a big pistol, but a pistol just the same. My sample came in a nice carrying case, with just one (sigh) 30-round magazine, a cable lock, owner’s manual and a sample packet of Lucas Extreme Duty gun oil – enough for a couple uses. This is a 9mm pistol, and once again, it is a PISTOL, with an 8-inch long barrel that is made out of carbon steel. Overall length of the gun, is 17-inches, and while SIG-Sauer says it has a mil-spec trigger pull, my sample pistol’s trigger was outstanding, and smooth.

The receiver is forged aluminum, and hard-coat Anodized for a long-lasting finish on it. At first glance, the MPX appears to be a miniature AR-15 firearm. It even has an ambidextrous charging handle on the top of the receiver – just like an AR has. The operating system is via a gas piston, for total reliability. My sample came with a set of pop-up sights on the top of the receiver, but you can add a nice red dot sight on the upper if you want – highly recommended. The accessory rail is of the KeyMod type – a rock-solid design for accessories. The pistol grip is polymer and comfortable.

There is also a single point sling that came with the set-up, and it attaches to the rear of the receiver. However, there are now several types of arm or wrist braces you can attach to the gun for a more stable hold on the gun. This just “complicates” matters, at least as far as the BATFE is concerned…with just the single point sling, there isn’t much to complain about. But the BATFE will surely get around to saying that the single point sling, somehow turns this pistol into a short-barreled rifle.

The MPX operates from a closed bolt, so the BATFE approved it. (Open-bolt guns are deemed too easy to convert to full auto.) All controls are in the same familiar places, the ambidextrous safety, bolt release, etc., as an AR-15 is. The bolt itself is a rotating version – again, a very reliable design in my opinion. SIG designed the MPX to run with all types and weights of 9mm ammo, so there is no need to adjust the short-stroke gas pistol, nor is there any adjustments to do so. At the end of the barrel, there is an AR-type flash suppressor. On the underside of the handguard is a “stop” so your off-hand can’t slip in front of the barrel – a very nice stop it is. On some similar types of pistols, the stops are very short and you can easily push your hand beyond the stop, in front of the barrel, for a very nasty surprise – something you don’t want or need.

My Earlier Tests

When I first tested the MPX, several years back, we didn’t have an ammo shortage, like we have today, so I fired more than 1,000-rds of various 9mm ammo through this gun. All ammo was from Black Hills Ammunition and if you check their website, you can see all the ammo I tested, including their HoneyBadger loads – and I had absolutely zero malfunctions of any type with all the different ammo. That is outstanding reliability – then again I didn’t expect any problems from the MPX.

Recent Accuracy Tests

I didn’t see any sense in taking the MPX out again, for another reliability test. However, I did do an accuracy test, with several types of Black Hill ammunition. The MPX really loved the 124-gr JHP load, and at 25-yards, with the gun over a padded rest, I could easily get 1.5-inch groups if I took my time. I only fired 5-rounds of each type of Black Hills ammo, because of the ammo drought, however all groups were easily under 2-inches. The 30-round included magazine operated smoothly and it wasn’t all that difficult to fully load it to full capacity.

A word on the magazines: Like all magazines from SIG-Sauer, they are expensive – I checked around, and these 30-round magazines are selling for $64 and up, when you can find them. However, bite the bullet and buy as many as you can afford to buy, because I believe, very soon, you won’t be able to get these mags, and will be stuck with only 10-rounders.

They’re Hard To Find

You won’t find many of the MPX pistols in gun shops these days, so its best to check out on-line sellers, like and other websites. A quick glance will show the MPX selling for $1,500 and up – again, if you can even find one of these guns. And, if you want one, don’t hesitate of think on it – buy the gun now, because next time you check, it will be sold.

I wish some aftermarket magazine maker would come out with some reliable 30-round magazines for the MPX, but to date, no one has – at least I haven’t found any. If you purchase the SIG-made magazines, and you can find them for $64 each – I would recommend getting no less than 10 of them – and that will set you back at least $640. However, in the end, you’ll be happy to got them…once the iron fist of gun control comes down, you won’t be able to get mags – at any price.

In closing, the MPX is an outstanding firearm, for home defense, plinking or just target shooting. It would get an outstanding SHTF weapon as well, it only weighs 5.5-pounds, and is easy to shoot, and easy to move through a building with – even one with narrow hallways and small rooms. I did a lot of building clearing, when I worked for an alarm company many years ago…on the day shift, I installed alarms, on the night shift, I answered alarms. A least 9-times out of 10, I would get to an alarm, long before the Chicago Police Department did. And, given that, most who responded, would tell me to go into the building to do a search – all by myself, while they “secured” the outside of the building. I lost count of the number of burglars I caught by myself, and the PD almost always took credit for the arrests. And, there is one thing I learned, and that is there is NO good way to do a building search by myself. However, I did learn a lot about searching buildings, just the same.

I would have loved to have had something like the SIG-Sauer MPX, in my hand, when searching giant warehouses and trucking docks, instead of a revolver. There were several jobs I’ve done over the years, when something like the MPX would have sure made me feel a lot safer. So, check one out, if you can find one, or find one on-line and snap it up, you’ll really be pleased with it.