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.
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.
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.
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.
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.
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.
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.
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.
Handguard- M Lok
Operating System- Short stroke piston
Capacity- 10, 20 or 30 rounds factory (+10 rounds extensions available)
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.
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.
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.
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.
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.
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.
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