(6 customer reviews)



The MPX Copperhead features a monolithic Elite Series Cerakote® finish upper receiver, with an integrated stock knuckle lower, and a 3.5” barrel with integrated muzzle brake. The MPX Copperhead comes equipped with the new SIG SAUER Pivoting Contour Brace (PCB) giving pistol users a brace that easily adapts to the movement of the shooter’s arm with a patented swivel operation for perfect placement, and can be rapidly deployed.

Unconventional design, unmatched performance, and familiar AR handling. The SIG MPX redefines the submachine gun category with a new level of operator safety, in-field adaptability and proven reliability in the harshest environments. Completely ambidextrous, the SIG MPX is great for left- or right-handed shooters with its dual-sided selector switch, magazine release, charging handle and bolt release. The SIG MPX operates from a fully-closed and locked rotating bolt, offering enhanced reliability and safety in use. A short-stroke gas piston allows the SIG MPX to run all weights and brands of 9mm ammunition with no adjustments to the gas valve.


Mag Type MPX
Barrel Length 3.5 in (89 mm)
Caliber 9mm Luger
Height 8 in [203 mm]
Overall Length 14.5 in [368 mm]
Overall Width 2.4 in [61 mm]
Twist Rate 1:10
Weight 4.5 lb (2 kg)
Operating System Gas Piston

sig mpx copperhead

Before we get to the new SIG Copperhead, let’s look at how we got to the latest MPX line entry. When first unveiled the MPX a few years ago, everyone in the gun world did a double-take. Here was a truly next-gen submachine gun that allowed you to switch barrels and configurations, and SIG quickly followed up with semi-auto versions. Consider it a beautiful sendoff to the HK MP5.

The MPX’s groundbreaking modularity led to other successful platforms, like SIG’s MCX and P320 series. And then you had other MPX variants, including the MPX-K, the shortest of the bunch like the hallowed MP5K. Until now.

Enter the SIG Copperhead

Another entry in the manufacturer’s “snake” series behind the MCX Rattler, the new SIG Sauer MPX Copperhead is exceptionally compact with a height of 8 inches and an overall length of just 14.5 inches. That’s incredible. What’s more, this 4.5-pound stunner is configured as a pistol, so just about everyone can get their hands on this covert powerhouse. The nitrided, 3.5-inch barrel has a unique integral flash suppressor. Meanwhile, the upper receiver is one monolithic design with a short forend area and a built-in hand stop.

At the rear you’ll find a stabilizing brace that rides on two rails and allows for two positions: Fully extended or fully retracted. Either way, when you’re firing this thing, you’ll naturally snug up on it, with your support hand wrapped around the magazine well. You’ll also find ambidextrous controls, a very cool PDW pistol grip and a polished single-stage trigger, all left black to contrast with the receivers and brace.

And what a contrast! The upper and lower receivers both sport a copper-like Cerakote E190 finish that closely matches the color of the arm brace. Also, along with increasing the pistol’s durability and corrosion resistance, the finish helps the MPX Copperhead stand out — or blend in — depending on your environment. Might not seem like much, but it really is a nice touch.


I was lucky to get my hands on a prototype at the 2018 in Montana this October. With a SIG ROMEO4T red-dot sight mounted on the top rail, it was hard to miss steel targets at 25 and 50 yards. After a brief learning curve, the Copperhead’s speed became apparent. This thing turns on a dime, like it was born for quick transitions between targets.

So stay tuned for future coverage on the MPX Copperhead. SIG says it expects shipping to begin in January. For more information, keep your eyes on

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