August 18, 2020
By James Tarr
SIG’s MPX was originally designed as a submachine gun, but SIG has seen more success selling pistol and carbine versions of this interesting design. The smallest is the 3.5-inch-barreled Copperhead pistol. The largest is the new MPX PCC, a 9mm carbine intended for PCC (pistol caliber carbine) competition, and right now it’s hard to find a hotter segment of the shooting market than PCCs.
The MPX PCC has a 16-inch barrel that is tipped with a three-port muzzle brake. It free-floats inside a 15-inch aluminum handguard with M-Lok accessory slots at three, six and nine o’clock.
From its appearance many people might describe the MPX as a “pistol-caliber AR,” but that description is not as accurate as you might think. While it will accept a few AR parts, the MPX is a completely unique design from the inside out.
Instead of having a direct-gas-impingement operating system like most rifle-caliber ARs or being a straight blowback gun like most pistol-caliber ARs, the MPX uses a proprietary short-stroke gas piston system. This operating system reduces reciprocating weight, reducing recoil.
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The controls are ambidextrous, and the crisp Timney trigger is a big improvement over the trigger found in the older MPX competition shooters used to flock to. All the AR-style controls on the lower receiver, as well as the charging handle, are ambidextrous. The stock is five-position adjustable for length, and it folds to the left side as well. There is a detent so it stays in the folded position. There is no buffer tube, so the MPX can be fired with the stock folded if you want extra credit for style points.
Over the past few years, an older version of the MPX was a preferred pistol-caliber carbine among serious competitors. They liked its large integral magazine well, but it was chosen among gamers mostly for its low recoil. That low recoil was due both to the SIG’s heavy-for-class weight and short-stroke piston operating system. However, as it came from the factory, that MPX carbine was far from perfect for competition.
First, it was too heavy, but the new the PCC sports a lightened handguard that brings the center of gravity back and the weight down to six pounds, 14.5 ounces. Second on the list of needed improvements was a better trigger pull. Most of the factory MPX trigger pulls were north of six pounds and gritty. By contrast, the single-stage flat-faced Timney trigger on my sample of the new MPX PCC sample weighed in at 4.75 pounds. It was very crisp with a short reset and little overtravel.
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The MPX PCC sports a folding stock, which is great for storage and transportation. Since there’s no buffer tube, it can be fired in this configuration as well. The MPX comes with one 30-round translucent magazine made by Lancer, but nobody who shoots a PCC in competition runs a standard-capacity magazine. Reloading takes time, and you don’t want that in a game where you are scored in points per second. For part of my testing, I used a +11 base pad made by TTI for 41 rounds of ammo onboard.
You’ll want additional magazines, and while they’re not cheap ($67 apiece, no matter the capacity), they are reliable. Shooting the MPX reminded me why it is the go-to for serious hosers: Recoil is almost nonexistent. The great trigger allowed me to shoot up to the gun’s accuracy potential and my speed potential.
Unless you are competing at a dedicated PCC match, PCCs are run on the same stages as pistols, which means most of your shots will be well inside 20 yards. As a result, pretty much everybody runs a non-magnified red dot on their PCCs. For testing and just general fun, I mounted a new Trijicon SRO on the PCC using Trijicon’s QD flattop RMR mounts for the sight.
The other big improvement from the previous version is the lighter fore-end, which not only lessens weight but moves the balance point toward the shooter. Here’s an interesting fact about 9mm carbines and competition. Competition shooters load their pistol ammo as soft as possible to reduce recoil in their pistols, but PCCs actually work better with hotter ammo. Lighter bullets pushed faster generate more gas for that muzzle brake, and the result, counterintuitive as it sounds, is hotter ammo makes the gun shoot flatter. That’s why Federal’s dedicated Syntech PCC load (a 130-grain bullet at roughly 1,130 fps) gives you a 145 power factor, far above the minimum 125 needed.
Over the past few years I have come to believe that pistol-caliber carbines are perhaps the best choice for home defense for most people. They’re easier to aim than a handgun, are far quieter than a rifle even with a muzzle brake, and hold lots of bullets.
With its big price tag and purpose-built design, the new MPX isn’t aimed at beginning shooters or the average person interested in home defense, but that’s not to say that it can’t perform double-duty as both a competition gun and home defender.
SIG Sauer MPX PCC Specs Type: Short-stroke gas piston semiauto centerfire Caliber: 9mm Luger Capacity: 30-round magazine supplied Barrel: 16 in., 1:10 twist, SIG 3-port muzzle brake Overall Length: 35.25 in. Weight: 6 lb., 14.5 oz. Receiver: 7075-T6 anodized aluminum Furniture: Folding five-position adjustable stock, SIG pistol grip, 15 in. M-Lok aluminum fore-end Trigger: Timney single-stage, 4.75 lb. pull (measured) Sights: Flip-up polymer Price: $2,016 Manufacturer: SIG Sauer, SIGsauer.com SIG Sauer MPX PCC Accuracy Results Notes: Accuracy results are the averages of four five-shot groups at 50 yards from a sandbag rest. Velocities are averages of 10 shots measured with an Oehler Model 35P 12 feet from the muzzle. Abbreviations: FMJ, full metal jacket
