King of the PCC’s – SIG’s MPX (New Model Review)

The Sig MPX made a significant splash in the Pistol Caliber Carbine (PCC) competition world when it was first released in 2015. Several top shooters adopted it over the 9mm AR-15 conversions and dedicated AR platform guns being used.  Both the AR style guns and the MPX were tweaked and upgraded by the shooters to gain an edge in the Practical Shooting arena where performance is measured down to the hundredth of a second.

Pistol Caliber Carbine (PCC) upgrades make MPX more at home on the range for speed and competitive shooting

Sig responded to the customer’s needs by releasing the MPX PCC in November 2018 with upgrades to make their platform competition ready directly from the factory. Input from the members of Sig’s shooting team and influences from the practical shooting community are obvious in the performance enhancing upgrades.

Compensator is designed to minimize weight added to muzzle allowing for rapid target transitions

The lightweight contour 1:10 twist 16 inch barrel now sports a three chamber compensator to help reduce the already minimal recoil generated by the 9mm carbine. The simple but effective design works well, keeping the muzzle steady allowing faster follow-up shots on target. The 9mm round only has a small amount of exhaust gas and pressure to work with compared to rifle rounds, but when competing at the highest levels every bit helps.

The trigger and the accuracy of the barrel/ action are two of the most important factors in the overall performance of a firearm. The MPX PCC comes from the factory with a Timney single stage trigger. This isn’t one of Timney’s super light precision long range type triggers. It’s a robustly built trigger to stand up to the punishment that the rapid cycling PCC bolt dishes out while still providing a reasonable pull to allow fast accurate shooting. The trigger weight averaged out at 4 lbs 13 ounces after 10 cycles on my Lyman Electronic Trigger Scale.

The little Nightforce 2.5-10x may be overkill for the 9mm but it made group testing a breeze to find true accuracy

I found the accuracy of the Sig PCC barrel/ action to be fantastic. Accuracy testing was done at 50 yards off the bench supporting the gun on a couple Armageddon Gear range bags. The gun was shooting so well that I feared the red dot sight might be holding back the results so I mounted a Nightforce 2.5-10x scope and continued the testing.

Top quality ammunition often brings the best accuracy

The smallest 5 shot group was a 1.24” delivered by Hornady 115 FTX Critical Defense ammunition.  The lower price point Hornady American Gunner 115’s pulled a second-place finish at 1.38”. Even the military ball ammunition consistently managed sub 3” groups. This gun isn’t going to be limiting your ability to hit your targets at any PCC matches.

Accuracy seemed more dependent on individual bullet design than favoring a particular bullet weight

Another factor I consider important is how a gun feels. It doesn’t matter how well it looks, how accurate it is, how reliable, or how light and fast a trigger resets if the gun feels like a brick in your hands you aren’t going to shoot it well. The MPX PCC feels great and it shows when you get it on the range. It points naturally and lends itself to making the rapid target transitions required in speed-based events.

Rail section along majority of the top of hand guard was removed to reduce weight and size

The new full length M-LOK handguard on the PCC model was a fantastic upgrade. It’s slim enough for small hands to easily and comfortably handle, and long enough to offer plenty of room for even the tallest shooters to take a forward grip on. At 15.5” long it has plenty of real estate for mounting lights, lasers or vertical grips. 

A subtle, but important feature of the handguard is that it has a slight downward flaring at the muzzle end that acts as a small hand stop. This keeps a shooter from putting their hand out too far and catching the muzzle blast from the compensator on their fingers.

The only negative I identified in the entire review of the MPX PCC is that the handguard appears to be a bit too long. It goes beyond the shoulder of the barrel and start of the threads making it impossible to mount a some other larger compensators or a suppressor.

At a bit over 6.5 pounds the MPX PCC levels the scales nicely between being light enough to move quickly and heavy enough to help control recoil. The PCC balances well with the mid-point being right at the forward takedown pin.

Support side magazine release will be a huge advantage for left handed shooters

Aiding the balance and fit is the side- folding adjustable stock. Besides the cool factor of the side-folder swinging away for easy storage and carry; the adjustable length allows tailoring the length of pull for balance, shooter comfort and shooting style. The buttstock locks in one of 5 positions with the length of pull ranging from 11” to 13.5”. The buttstock also has two mounting points for a sling.


Caliber- 9mm


Handguard- M Lok

Operating System- Short stroke piston

Capacity- 10, 20 or 30 rounds factory (+10 rounds extensions available)

Trigger- Timney

Weight- 6 lbs 10 oz

Length- 26.5” (Folded), 33” (Open collapsed), 35.25” (Open extended)

MSRP- $2016 (Steet price ~ $1699)

Due to its popularity the number of accessories for the MPX is growing. For shooters that favor a true AR15 style stock, Thorsden Customsoffers a buffer tube adapter that clamps to the rear of the MPX PCC receiver and allows mounting an AR buffer tube and associated stock of the shooters choice.

Operating system is easy to disassemble for cleaning and maintenance for aiding reliability

Perhaps the most important characteristic of a firearm that is more critical than all the rest is reliability. Will it shoot every time and keep running when you need it too? I shot well over 2000 rounds of mixed ammunition through the Sig PCC and only had two failures, and those were my fault. 

The only two rounds that failed to feed were a couple of my hand loads that were cranked out right before a match with a different bullet and didn’t have enough crimp to hold the bullet in place when driven forward by the bolt- my bad not the guns.

The short-stroked piston operated rotating bolt operating system is less finicky and more reliable than most of the PCC’s I’ve seen at the local matches. The Sig system just works; put a dot or scope on it, bullets in it and go to the range or match. The dual recoil springs are attached to the bolt carrier and the whole assembly reminds me of a combination between and AR bolt /carrier group, Ruger 10/22 and a Benelli Vinci operating system. Regardless of where the design originated, it’s simple, it works and it’s reliable.

Similar operating recoil systems from two very reliable firearm systems

Operating the PCC is simple as all the controls are similar to an AR-15. I say similar because the Sig has all ambidextrous controls so everything can be operated from either side of the gun-awesome. Even the charging handle has dual releases rather than just on one side; making it easier for cycling if needed under the always counting timer of life and competition.

Another subtlety I noticed is that the magazine release button is slightly farther away from the back of the grip on the PCC than on a standard AR15.  I had chalked up a couple of bad reloads during competition due to being new to the gun and the rush of match pressure. However, while handling the gun for pictures and gathering specs I noticed that the button felt like a bit more of a reach than normal, and it is. 

Ambi-contols and Timney flat trigger make PCC a natural for manipulation and shooting

It is about a ¼” further from the back of the grip to the rear edge of the mag release button on the PCC than an AR15, barely enough to notice but just enough to throw off a couple reloads for shooters with smaller hands until you focus on it and get used to it. 

Sig makes 10, 20 and 30 round magazines for the MPX. The shorter length of the 20-round version suited me the best for speed reloads. Several vendors such as  Taran Tactical Innovations make magazine extensions to further increase capacity minimizing the need for reloads at all.

Magazines, regardless of capacity proved completely reliable during all testing


The Sig MPX PCC provided rock solid reliability, outstanding accuracy, handled well and was easy to shoot at speed or distance. The upgrades the PCC model provides leaves little else to be desired or needed prior to taking it to the range or match. 

Upgrades from lessons learned are blended in to the ultra-reliable platform for maximum performance

I shot the PCC at several local USPSA matches and actually won a couple with the Sig. The light weight and low recoil, along with the red dot for aiming made the gun a joy to shoot and it was a big hit with new and experienced shooters alike. The only problem with the MPX PCC is that it is so fun to shoot the magazines always seem to run out to soon.

Everyone who shot the PCC was amazed at how easy it was to successfully defeat the usually humbling plate rack at the range. Sig obviously listened to its Pro shooters and consumers and delivered another solid firearm. I wouldn’t hesitate to take the MPX PCC to any match in the country after just adding a good red dot sight.

Visit SIG to learn more by clicking HERE.

Visit SIG to learn more by clicking HERE.

***Shop GunsAmerica for your next SIG MPX PCC***

About the author: Jeff Cramblit is a world-class competitive shooter having won medals at both the 2012 IPSC World Shotgun Championship in Hungary and more recently the 2017 IPSC World Rifle Championship in Russia. He is passionate about shooting sports and the outdoors. He has followed that passion for over 30 years, hunting and competing in practical pistol, 3gun, precision rifle and sporting clays matches. Jeff is intimately familiar with the shooting industry – competitor, instructor, RO, range master, match director. Among his training credits include NRA Instructor, AR-15 armorer, FBI Rifle Instructor, and Officer Low Light Survival Instructor. As a sponsored shooter, Jeff has represented notable industry names such as: Benelli, 5.11 Tactical, Bushnell, Blackhawk, DoubleStar, and Hornady. He has been featured on several of Outdoor Channel’s Shooting Gallery episodes and on a Downrange TV series. Jeff’s current endeavors cover a broad spectrum and he can be found anywhere from local matches helping and encouraging new shooters as they develop their own love of the sport, to the dove field with his friends, a charity sporting clays shoot, backpack hunting public land in Montana, or the winners podium of a major championship.

{ 8 comments… add one }
  • Matthew Steven Cuddy June 17, 2019, 5:04 pm

    Oh god, another nine millimeter. I guess if you get some hotted up 9mm rounds they can almost knock someone out of their sandals. As an offensive pistol round, the 9mm is not up to the task of stopping someone with a first shot. This has been proven in both Iraq and Afghanistan. Unless it’s a CNS hit, the target will keep going.

    Shot in the chest, the leg or the big toe a .45 auto will stop you, and put you on the ground. My nephew had a tour in Iraq, and all the special forces folks were strapped with a .45 automatic, most modified to accept a 12 round magazine. When Ian asked one of the special forces billeted in his room, in jest he asked the Ranger why they carried an obsolete pistol, the Ranger laughed and said “This pistol is the original bad ass.”

  • Bob June 17, 2019, 12:43 pm

    The review would have been more useful if it had evaluated whether significant problems with previous MPX’s had been fixed: broken firing pin (or was it ejectors?), slop in the cocking handle causing wear and tear on the receiver edges just under the cocking handle, the infamous ringing muzzle brake, etc.

    And the length of the barrel shroud preventing use of a suppressor is a major screw up. All this for, what, close to to $2,000?

    I have no dog in this fight, but from my evaluation of a used MPX and research into the past problems with SIG longguns, you won’t find me being an early adopter.

  • Dick Riggar June 17, 2019, 11:52 am

    It sure is good to see your name and read some about you.
    I hope you’re doing well and feeling good.

    (x) Palmetto Gun Club

  • Evan June 17, 2019, 11:51 am

    I completely fail to understand the need for a 9mm carbine.

    Now, I’m not one of those people who claims 9mm is useless – it isn’t, and my carry gun of choice is a Glock 19. But I am going to say that 9mm is only good as a pistol round. You start putting it in a carbine, and you end up with not enough round for too much gun. It’s like having an M82A1 chambered in .308 or something – too much gun for what you’re getting.

    With the popularity of short barreled 5.56 or .300BLK carbines, I tend to think that pistol caliber carbines are obsolete no matter what – if I have the money to spend on a SIG carbine, I’m going MCX Rattler over MPX ten times out of ten. But if you insist on making carbines in pistol calibers, why not just make it a 10mm? With a 10mm, you’re at least getting the kind of performance that can justify that much gun. Lesser calibers – 9mm, .40 Short & Weak, .45ACP, etc, just don’t.

    So basically – don’t make PCCs, because they’re lame and don’t do anything a 5.56 or .300 Blackout can’t do as well or better, and if you do make a PCC, make it in 10mm. Otherwise there’s just no point.

    Someone I bought a rifle from a few months back was telling me that he had an MPX, and that it was amazingly fun to shoot though.

    • I Love Liberty June 23, 2019, 7:22 pm

      I agree. $1,700 for a pistol caliber carbine is overpriced. I do have a 9 millimeter upper assembly for an AR-15. It cost $450 for the 9 millimeter upper assembly and Colt magazine well conversion. The two twenty and extra thirty-two round magazines cost about another $70. I use the 9 millimeter Luger upper assembly for training mainly because the ammo is so cheap. It is about $10.75 for fifty rounds of 9 millimeter Luger and about $14 for twenty rounds of .300 AAC Blackout.

      I can switch out the AR-15 upper assembly in about one minute and then shoot .300 AAC Blackout which is a real rifle round.

      In all my total costs for a .300 AAC Blackout with about ten thirty round magazines and a 9 millimeter Luger upper assembly with another three magazines was about $1,330.

      I get two rifle calibers for less cost than this Sig MPX for $1,700 with thirteen standard capacity magazines.

  • mike nason June 17, 2019, 9:47 am

    ANOTHER 9mm carbine – why? Where is the 10mm?

  • Larry Hampton June 17, 2019, 8:50 am

    Great article. Gave me a lot of good info, most of which applies to my new MPX Copperhead. Hopefully Timney makes a trigger for the Copperhead or the same one will work.

  • Fred Galas June 17, 2019, 6:58 am

    I agree with the author concerning the excessive hand guard length. Seeing that most competitors will be using an electronic sight, the extended sighting plane is not needed and just adds weight.

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