Sig Sauer MPX Review: 1,500 Round Test of the Premium PCC (2026)

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Review: Sig Sauer MPX – The Porsche of Pistol-Caliber Carbines

Our Rating: 8.8/10

The Sig Sauer MPX is the pistol-caliber carbine that every other PCC gets measured against. It’s also the one that makes your wallet cry. After 1,500 rounds (suppressed and unsuppressed), I can tell you the MPX earns its reputation as the best-shooting PCC on the market. Whether it earns its $1,800+ price tag depends entirely on what you value.

• RRP: $1,899-$2,199 (varies by model)
• Street Price: $1,800-$2,200 (Check our live pricing for the best current deal)
• Caliber: 9mm Luger
• Action: Locked-breech, short-stroke gas piston
• Barrel Length: 8″ (MPX K) / 16″ (MPX PCC Carbine)
• Overall Length: 22.75″ collapsed / 25.25″ extended (K) | 35.25″ (Carbine)
• Weight (unloaded): 6.3 lbs (K) / 6.6 lbs (Carbine)
• Capacity: 30+1 (proprietary Sig MPX magazines)
• Receiver Material: 7075-T6 aluminum (hard-coat anodized)
• Handguard: Full-length M-LOK
• Stock: Folding/collapsing (K/PDW), fixed or telescoping (Carbine)
• Trigger: Sig match trigger (Timney aftermarket option)
• Sights: None (full-length Picatinny top rail)
• Safety: Ambidextrous selector
• Suppressor-Ready: Yes (1/2×28 threaded barrel)
• Made in: USA (Sig Sauer, Newington, NH)

Quick Take: Sig Sauer MPX Review

I’ll be honest with you. The Sig Sauer MPX is one of the best pistol-caliber carbines I’ve ever shot. It’s also the hardest one to recommend, because it costs nearly twice what the next best option runs. That’s the tension at the heart of this review, and I’m not going to pretend it doesn’t exist.

The MPX’s party trick is its short-stroke gas piston operating system. Every other mainstream PCC (CZ Scorpion, CMMG Banshee, Stribog) runs a simple blowback action. Blowback works fine, but it means a heavy bolt slamming back and forth with every shot. The MPX’s locked-breech gas piston system eliminates that. The result is a 9mm carbine that shoots flatter and softer than anything else in its class.

Over 1,500 rounds of mixed ammunition, the MPX never hiccupped once. Not with cheap 115-grain brass, not with 147-grain subsonic loads through a suppressor, not once. Zero malfunctions. That gas piston earns its keep.

Best For: Competition shooters, home defense builds, suppressor hosts, and anyone who wants the absolute best-shooting PCC regardless of cost. If you’re looking for a 9mm carbine that does everything at the highest level, this is it.

Why Sig Built the MPX This Way

To understand the MPX, you need to understand what Sig was trying to solve. When the MPX first appeared in 2015, the PCC market was dominated by blowback guns. AR-9 conversions, the CZ Scorpion, the Beretta CX4. They all worked the same way: a heavy bolt flies backward when the round fires, then a spring pushes it forward again. Simple, reliable, cheap to build.

The problem with blowback is physics. You need a heavy bolt to keep the action closed long enough for the bullet to leave the barrel. That heavy bolt slamming around creates felt recoil that’s disproportionate to the 9mm cartridge. Shoot an AR-9 back-to-back with an AR-15 in 5.56, and the AR-9 actually feels snappier. That’s blowback for you.

Sig’s solution was to build a miniaturized version of their MCX rifle platform. The MPX uses a true locked-breech, short-stroke gas piston system. The bolt locks into the barrel extension via rotating lugs, just like an AR-15. A gas piston taps gas from the barrel to cycle the action. This means the bolt can be lighter because it doesn’t need mass to stay closed. The result is dramatically less felt recoil.

It’s an expensive approach. There are more parts, tighter tolerances, and a more complex manufacturing process than a simple blowback tube gun. That’s why the MPX costs what it does. But the shooting experience is in a completely different league, and that’s why law enforcement agencies, military units, and competitive shooters keep choosing it.

The MPX also grew out of Sig’s contract work. Variants of this platform are in service with agencies worldwide. That military/LE pedigree isn’t just marketing fluff. It means the gun was designed to run hard, run dirty, and keep working when it matters.

MPX Variants: K, PCC Carbine, and Copperhead

Sig sells the MPX in several configurations, and the differences matter more than you’d think. Here’s what you need to know about each one.

MPX K (8″ Barrel)

This is the one most people want. The MPX K ships with an 8-inch barrel, a folding/collapsing PDW-style brace or stock (depending on configuration), and an M-LOK handguard. It weighs 6.3 pounds unloaded. Collapsed, it’s just 22.75 inches long. That’s small enough to fit in a backpack.

The K model is the best all-around choice for most buyers. It’s compact enough for home defense, light enough for competition, and the 8-inch barrel gives you enough velocity to make 9mm perform properly. If you’re going to suppress it (and you should, because the MPX suppressed is an experience), the K is the one to get. Street prices typically land between $1,800 and $2,000.

MPX PCC Carbine (16″ Barrel)

The 16-inch carbine version is built for PCC competition. The longer barrel squeezes every bit of velocity out of the 9mm cartridge, and the fixed stock gives you a more stable shooting platform. It weighs 6.6 pounds and has a 35.25-inch overall length. This is the configuration that dominates USPSA PCC division.

If you’re primarily a competition shooter, the carbine makes sense. For everyone else, the K is the better buy. The carbine gives up the compactness that makes the MPX special, and at that size, you’re in direct competition with full-size rifle platforms.

MPX Copperhead (3.5″ Barrel)

The Copperhead is the ultracompact variant with a tiny 3.5-inch barrel and a monolithic upper receiver. It’s the smallest MPX and looks like something out of a John Wick movie. Sig designed it with a reduced-size receiver and a 20-round flush-fit magazine for maximum concealability.

I’d steer most buyers away from the Copperhead. The 3.5-inch barrel sacrifices a lot of velocity (you’re barely getting more than a long-slide pistol at that point), and the proprietary Copperhead magazines don’t work in the standard MPX. It’s a cool range toy, but the K does everything better at a real-world distance.

Competitor Comparison

The MPX lives in a competitive market. Here’s how it stacks up against the PCCs you’re probably cross-shopping.

CZ Scorpion Evo 3 (~$899)

The CZ Scorpion is the people’s PCC. At roughly half the price of the MPX, it does about 80% of what the Sig does. The Scorpion runs a simple blowback action with a polymer lower and aluminum upper. It’s reliable, has a decent aftermarket, and CZ’s build quality is solid.

Where the Scorpion falls short is recoil and trigger. The blowback action creates noticeably more felt recoil than the MPX’s gas piston system. The factory trigger is mushy and heavy (though aftermarket triggers from HBI and Shooter’s Element fix this for $40-80). If you’re on a budget and want a PCC that works well, the Scorpion is the smart buy. If you want the best shooting experience, the MPX wins. Check out our full CZ Scorpion Evo 3 review for the deep dive.

B&T APC9 (~$2,400)

The B&T APC9 is the Swiss-made alternative that splits the difference between the MPX and HK SP5. It’s a blowback design, but B&T uses a hydraulic buffer system that tames the recoil surprisingly well. Build quality is exceptional. The APC9 Pro accepts Glock magazines, which is a real advantage over the MPX’s proprietary mags.

At $2,400, the APC9 is more expensive than the MPX while using an inferior operating system. You’re paying for Swiss manufacturing and the non-reciprocating charging handle. It’s a great gun, but I’d take the MPX’s gas piston over the APC9’s hydraulic buffer every time. The Glock mag compatibility is the APC9’s strongest argument.

HK SP5 (~$2,800)

The HK SP5 is the civilian version of the legendary MP5. If you grew up watching action movies in the ’80s, you’ve dreamed of owning one. The roller-delayed blowback system is smoother than direct blowback, though not as smooth as the MPX’s gas piston. The SP5 has a certain cool factor that no other PCC can match.

At $2,800+, the SP5 is really a collector’s piece and nostalgia purchase more than a practical choice. The ergonomics feel dated compared to anything with AR-style controls. The magazine release is the classic HK paddle, the safety is stiff, and mounting optics requires aftermarket solutions. I love shooting the SP5, but I’d grab the MPX for anything serious.

Get the full SP5 review here.

CMMG Banshee Mk4 (~$1,300)

The CMMG Banshee Mk4 is the closest competitor to the MPX in terms of operating system. CMMG’s Radial Delayed Blowback isn’t a true locked-breech gas piston, but it’s a significant step up from straight blowback. The bolt rotates slightly to delay opening, reducing felt recoil. It also runs on standard AR-15 components, so the aftermarket is massive.

At $1,300, the Banshee gives you about 90% of the MPX’s shooting experience for about 70% of the price. The AR-compatible lower means you can use any AR trigger, grip, and stock. If I were building a PCC on a budget but couldn’t stomach a full blowback gun, the Banshee Mk4 would be my pick. The MPX still shoots softer, but the gap is smaller than you’d expect.

Technical Deep Dive

Gas Piston System

Let’s talk about what makes the MPX different from everything else. The short-stroke gas piston system taps propellant gas from a port in the barrel and drives a piston rearward. That piston strikes the bolt carrier, which then unlocks from the barrel extension and cycles rearward to extract and eject the spent case. A return spring pushes everything forward, stripping a new round from the magazine and locking the bolt back into battery.

This is fundamentally the same operating principle as an AR-15 or AK-47, just miniaturized for 9mm. The advantage is a lighter bolt carrier. Since the bolt locks into the barrel extension, you don’t need bolt mass to keep the action closed. Less mass moving back and forth means less felt recoil. It really is that simple.

The gas system also makes the MPX a far better suppressor host than any blowback PCC. Blowback guns don’t have a gas system to tune, so adding a suppressor (which increases backpressure) makes them cycle harder and feel snappier. The MPX’s adjustable gas block lets you tune the system for suppressed or unsuppressed shooting. Running suppressed, the MPX is absurdly quiet and smooth with 147-grain subsonic loads.

Upper and Lower Receivers

Both receivers are machined from 7075-T6 aluminum with a hard-coat anodized finish. The fit between upper and lower is tight with zero wobble on my test gun. Sig uses the same mil-spec Type III anodizing process as their military rifles, and it shows. The finish is uniform and resists wear well.

The upper receiver has a full-length Picatinny rail for optics mounting. The monolithic design (rail is integral to the upper) provides a solid, repeatable mount. I ran a Holosun 510C for most of my testing and never had to re-zero after removing and reinstalling it.

M-LOK Handguard

The MPX ships with Sig’s proprietary M-LOK handguard. It’s slim, lightweight, and has M-LOK slots at the 3, 6, and 9 o’clock positions. The handguard is free-floating, which contributes to accuracy. It also stays cool during extended shooting sessions since the gas piston keeps the heat at the gas block rather than dumping it into the handguard like a DI system would.

One note: the MPX handguard is not AR-15 compatible. You can’t swap on an aftermarket AR handguard. Sig and a few third-party manufacturers (Midwest Industries, Lancer) make MPX-specific handguards. Options exist, but they’re more limited and more expensive than AR alternatives.

Controls and Ergonomics

If you can run an AR-15, you can run an MPX. The controls are nearly identical: ambidextrous safety selector, ambidextrous magazine release, bolt catch/release on the left side, and a mil-spec charging handle. Everything is where an AR shooter expects it to be.

The ambidextrous controls deserve praise. Both the safety selector and magazine release work from either side without any aftermarket modifications. The safety is positive and tactile. The magazine release drops mags cleanly every time. Left-handed shooters will appreciate that Sig didn’t treat ambi controls as an afterthought.

The pistol grip is a standard AR-pattern grip, so you can swap it out for whatever you prefer. I replaced mine with a Magpul MOE-K2+ for the more vertical grip angle. Took about 30 seconds.

Trigger

The stock Sig trigger is serviceable but not spectacular. It’s a single-stage design with roughly 5.5 to 6 pounds of pull weight. There’s a bit of creep before the break, and the reset is audible but not as crisp as I’d like. For a duty or home defense gun, it’s perfectly fine. For competition, you’ll want to upgrade.

The Timney MPX trigger is the gold standard upgrade. It drops in without modification and gives you a clean, 2.5-pound single-stage pull with a glass-rod break. The difference is transformative. If you’re running the MPX in competition, the Timney is a must-buy. Budget about $200 for it.

Folding Stock (K Model)

The MPX K’s folding and collapsing stock is one of its best features. It folds to the right side of the receiver, bringing the overall length down to just 14.5 inches (without a muzzle device). That’s small enough to stash in a messenger bag or laptop case. The stock locks solidly in both the folded and extended positions with no wobble.

Unlike some folding-stock designs, the MPX will fire with the stock folded. The gas piston system doesn’t care about stock position. This is a genuine advantage for vehicle deployment or extremely tight quarters. The stock deploys quickly with a push of the latch, and it’s intuitive enough that you can do it one-handed with practice.

Magazines

This is where the MPX takes its biggest hit. Sig uses proprietary translucent polymer magazines that cost $50+ each. They’re excellent magazines: reliable feeding, clear body so you can see round count, steel feed lips, and they drop free cleanly. But $50 per magazine adds up fast when you’re stacking mags for competition or training.

For comparison, CZ Scorpion magazines run about $20-25, and Glock 33-round mags (which work in the CMMG Banshee and B&T APC9 Pro) are about $30. Over 10 magazines, you’re paying $200-250 more for the MPX ecosystem. That’s not nothing. Lancer also makes MPX-compatible magazines, but they’re similarly priced.

At the Range: 1,500 Round Test Protocol

I put 1,500 rounds through the MPX K over four range sessions spanning about six weeks. The goal was to test reliability across a wide range of ammunition, evaluate accuracy at realistic PCC distances, and spend significant time shooting suppressed. Here’s exactly what I ran.

Ammunition Log

• Winchester White Box 115gr FMJ: 400 rounds
• Federal American Eagle 124gr FMJ: 300 rounds
• Blazer Brass 115gr FMJ: 250 rounds
• Federal Syntech 150gr TSJ: 150 rounds (suppressed)
• Hornady Sub-X 147gr: 150 rounds (suppressed)
• Speer Gold Dot 124gr +P JHP: 100 rounds
• Federal HST 147gr JHP: 100 rounds
• S&B 124gr FMJ: 50 rounds

Total: 1,500 rounds. Malfunctions: Zero.

Break-In Period

The MPX needed no break-in. From the very first magazine of Winchester White Box, the gun ran perfectly. The gas piston cycled smoothly, the bolt locked back on the last round every time, and magazines dropped free without hesitation. Some gas piston guns need a few hundred rounds to smooth out. This one didn’t.

I intentionally started with the cheapest ammo I could find to stress test the system early. If a gun is going to choke, it’ll usually be on budget 115-grain loads. The MPX ate them without complaint.

Reliability Testing

I kept a detailed log of every malfunction. There weren’t any. Zero failures to feed, zero failures to eject, zero failures to lock back, zero light strikes. Across 1,500 rounds of seven different loads from four manufacturers, the MPX was mechanically perfect.

I also tested with the gun deliberately dirty. After 600 rounds without cleaning, the action was visibly carbon-fouled. It didn’t care. The gas piston system is inherently cleaner than a direct impingement AR because the piston keeps carbon out of the receiver. Even after 600 rounds, the bolt carrier group was dirty but functional.

The only intentional malfunction test I ran was shooting with a weak grip to simulate limp-wristing. This is irrelevant for a shoulder-fired weapon, but I was curious. No issues whatsoever, as expected from a gas-operated system.

Accuracy Testing

Accuracy testing was done at 25 and 50 yards from a rest, using a Holosun 510C red dot. At 25 yards, the MPX K consistently produced 1.5 to 2-inch groups with 124-grain Federal American Eagle. The best group of the day was 1.2 inches with Hornady Sub-X 147-grain loads. For a pistol-caliber platform with an 8-inch barrel, that’s outstanding.

At 50 yards, groups opened to 2.5 to 3.5 inches depending on the load. The heavier 147-grain bullets grouped tighter than the lighter 115-grain loads at this distance. The locked-breech system gives the MPX a genuine accuracy advantage over blowback PCCs. In a blowback gun, the bolt starts moving before the bullet leaves the barrel. In the MPX, the bolt stays locked until gas pressure operates the piston. That matters at distance.

Practical accuracy (shooting quickly at steel from various positions) was excellent. The flat-shooting nature of the gas piston system meant fast follow-up shots landed where I expected them. Transitions between targets were quick because the gun doesn’t move much during the firing cycle.

Suppressed Testing

This is where the MPX truly separates itself. I ran 300 rounds suppressed using a SilencerCo Omega 9K, split between 147-grain Hornady Sub-X and 150-grain Federal Syntech. The experience was revelatory.

With the gas block adjusted for suppressed shooting, the MPX was hearing-safe with subsonic loads. The action noise was louder than the muzzle report. Felt recoil was almost nonexistent. I’m not exaggerating when I say it felt like shooting a .22 LR. The combination of the locked-breech action and subsonic ammunition creates a shooting experience that’s genuinely difficult to describe to someone who hasn’t tried it.

Blowback PCCs running suppressed get louder at the ejection port because the increased backpressure forces the bolt open more violently. The MPX’s gas piston eliminates this. Gas doesn’t blow back through the action. The adjustable gas block keeps everything running at the optimal speed. If you own or plan to own a suppressor, the MPX is the best PCC host you can buy.

Performance Testing Results

Reliability: 10/10

Perfect reliability across 1,500 rounds of mixed ammunition. The gas piston system is mechanically superior to blowback for reliability because it provides consistent bolt velocity regardless of ammunition power factor. Cheap 115-grain loads cycle the same as hot 124-grain +P. I have zero reliability concerns with the MPX.

The gas system’s self-regulating nature also means the MPX should maintain this reliability over tens of thousands of rounds. There’s no heavy bolt battering the receiver on every shot like a blowback gun. Component longevity should be excellent.

Accuracy: 9/10

The locked-breech design provides a measurable accuracy advantage over blowback PCCs. 1.5 to 2-inch groups at 25 yards from a rest is impressive for any 9mm platform, especially one with an 8-inch barrel. The consistency across different loads was also noteworthy. Even budget ammunition grouped well.

I’m docking one point because the 8-inch barrel limits the MPX K’s effective range compared to the 16-inch carbine variant. The 16-inch model will stretch the 9mm further. But for what the K model is designed to do (inside 100 yards), the accuracy is more than sufficient.

Ergonomics and Recoil: 9/10

The MPX has the softest recoil of any PCC I’ve tested. Period. The gas piston system reduces felt recoil by roughly 30-40% compared to a blowback PCC shooting the same ammunition. Follow-up shots are faster and more accurate because the gun doesn’t move as much during the firing cycle.

The AR-style controls mean any AR shooter can pick up the MPX and run it immediately. Magazine changes are fast and intuitive. The folding stock on the K model is rock solid and deploys quickly. The only ergonomic knock is the weight. At 6.3 pounds unloaded (closer to 7 pounds with a loaded 30-round mag, optic, and light), the MPX is heavier than some of its competitors. The CZ Scorpion, for example, is about a pound lighter.

Fit, Finish, and QC: 9/10

Sig’s build quality on the MPX is excellent. The anodizing is uniform and durable. The upper-to-lower fit is tight with no play. The charging handle is smooth. The gas block is properly aligned. My test gun showed no signs of quality control issues.

The overall impression is of a professional-grade tool. Nothing feels cheap or aftermarket. The MPX exudes the kind of confidence that makes you understand where your $1,800+ went. Every surface, every control, every mechanical interaction feels intentional and well-executed.

Known Issues and Common Problems

Price

The elephant in the room. The MPX K starts around $1,800 at the best street prices, and some configurations push past $2,200. That’s serious money for a 9mm platform. By the time you add an optic ($250-400), a weapon light ($120-250), a suppressor ($400-800 plus the tax stamp), and a handful of spare magazines ($150-250), you’re looking at a $3,000+ setup.

Is the MPX twice as good as a CZ Scorpion? No. Is it noticeably better? Yes. Whether that “noticeably better” justifies the price premium is a personal decision. I think it does if you shoot suppressed or compete. If you just want a range toy PCC, the Scorpion or Banshee makes more financial sense.

Proprietary Magazines

At $50+ per magazine, building up a supply of MPX mags is expensive. You’ll want at least six magazines for a competition setup, which is $300 in magazines alone. Compare that to $150 for Glock mags or $120 for Scorpion mags. The MPX magazines are high quality, but the proprietary nature limits your options and inflates the cost of ownership.

Limited Aftermarket

The MPX has a decent aftermarket, but it’s nowhere near the AR-15 ecosystem. Handguard options are limited. Trigger options are essentially the Timney and nothing else worth mentioning. Charging handles, barrel options, and muzzle devices specific to the MPX exist but in fewer varieties and at higher prices than their AR equivalents.

This is improving over time as the platform gains popularity, but it’s still a consideration. If you’re someone who loves to tinker and customize, an AR-9 or the CMMG Banshee (which uses AR components) might be more satisfying.

Weight

At 6.3 pounds unloaded, the MPX K is heavier than some competitors. The CZ Scorpion comes in at 5.1 pounds, and some AR-9 pistols are even lighter. The gas piston system adds weight compared to a simple blowback bolt. You’re carrying that weight for the reduced recoil and improved reliability, but it’s worth noting if weight is a primary concern.

Early Generation Issues (Resolved)

The first-generation MPX (2015-2016) had some well-documented issues with bolt carrier cracking and gas system erosion. Sig redesigned the BCG and gas system for the Gen 2+ models, and these issues have been resolved. If you’re buying new in 2026, this isn’t a concern. If you’re buying used, make sure you’re getting a post-2017 model with the updated carrier.

Parts, Accessories, and Upgrades

The MPX doesn’t need much out of the box, but here are the upgrades that actually make a difference.

If you can only afford one upgrade, make it the Timney trigger. Nothing else transforms the MPX’s shooting experience as dramatically. The stock trigger is adequate, but the Timney makes the gun feel like it costs $3,000.

Shop for MPX accessories at EuroOptic and Brownells for the best selection and pricing.

The Verdict

The Sig Sauer MPX is the best pistol-caliber carbine you can buy. I’m comfortable saying that without qualification. The gas piston operating system delivers less recoil, better accuracy, and superior suppressor performance compared to every blowback PCC on the market. After 1,500 rounds of flawless reliability, I have absolute confidence in this platform.

But “best” and “best value” are different things. The MPX costs $1,800+ before you add a single accessory. Proprietary magazines are $50 each. The aftermarket, while growing, is still limited compared to AR-pattern guns. If you’re on a budget, the CZ Scorpion at $899 or the CMMG Banshee Mk4 at $1,300 will serve you well. You’ll feel the difference at the range, but you might not feel it enough to justify the premium.

If you shoot suppressed, compete in PCC division, or simply want the finest 9mm carbine money can buy, the MPX is worth every penny. It’s the Porsche of PCCs. You’re paying for engineering that you can feel in every shot. After 1,500 rounds, I get why competition shooters keep choosing this gun. Once you’ve shot a gas piston PCC, blowback feels crude by comparison.

Final Score: 8.8/10

Best For: Competitive PCC shooters, suppressor enthusiasts, home defense builds where budget isn’t the primary concern, and shooters who want the best 9mm platform available regardless of cost. Pairs exceptionally well with a quality suppressor and red dot for the ultimate close-range setup.

FAQ: Sig Sauer MPX

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Suggested FAQ entries:

• Q: Is the Sig Sauer MPX worth the price? A: The MPX is the best-shooting PCC on the market thanks to its gas piston system, but at $1,800+ it’s a premium purchase. It’s worth it for competition shooters, suppressor owners, and anyone who prioritizes the best recoil impulse. Budget buyers should consider the CZ Scorpion or CMMG Banshee instead.
• Q: Does the Sig MPX use Glock magazines? A: No. The MPX uses proprietary Sig Sauer magazines that cost $50+ each. This is one of the platform’s biggest drawbacks. The B&T APC9 Pro and many AR-9 platforms accept Glock magazines, which are cheaper and more widely available.
• Q: What is the difference between MPX K and MPX PCC? A: The MPX K has an 8-inch barrel with a folding/collapsing stock and is the compact model. The MPX PCC has a 16-inch barrel with a fixed or telescoping stock designed for competition. The K is better for home defense and suppressed shooting. The PCC is better for competitive PCC division.
• Q: Is the MPX a good suppressor host? A: The MPX is the best PCC suppressor host available. Its gas piston system and adjustable gas block let you tune for suppressed shooting, unlike blowback PCCs that can’t regulate backpressure. With subsonic 147-grain loads, the suppressed MPX is hearing-safe and incredibly smooth.
• Q: Sig MPX vs CZ Scorpion: which is better? A: The MPX is objectively the better gun with less recoil, better accuracy, and superior suppressor performance. The CZ Scorpion costs roughly half as much ($899 vs $1,800+) and does about 80% of what the MPX does. The Scorpion is the better value; the MPX is the better gun.
• Q: Does the Sig MPX have any known reliability issues? A: Early first-generation MPX models (2015-2016) had bolt carrier and gas system issues that Sig resolved in later production. Current-production MPX models are extremely reliable. In our 1,500-round test, we had zero malfunctions across seven different loads.