Light and modular, as per SOF requests
The new SIG Sauer MCX configures to meet many diverse needs. The MCX project started in 2011, and was designed to run with a suppressor to be military-reliable across multiple calibres. Multiple calibres across multiple barrel lengths is hard enough, but when adding the disparate pressure curves that come with using powders designed for both rifle and pistol cartridges in the same semiauto rifle, gun designers are faced with the proverbial Gordian Knot.
The company developed the MCX rifle for USSOCOM with the goal to build a firearm that is as quiet as an MP5, as deadly as an AK-47, and more modular than anything ever designed. Originally chambered in 300 AAC Blackout (BLK), the MCX is extremely controllable, according to Franz von Stauffenberg, CEO SIG SAUER GmbH & Co. KG, together with his US partner, Steve “Mato” Matulewicz, Executive Director Global Defense, SIG Sauer Inc., who showcased the weapon at SHOT Show 2017.
SIG Sauer’s design team made the SIG Sauer MCX light and modular, as per their clients’ guidance. They quickly settled on a piston system with dual recoil springs (piston systems are a great way to regulate the speed with which the action cycles because they can easily bleed off excess gases). By using two recoil springs, SIG disperses the load and gives each spring a longer service life than a rifle working off a single recoil spring. This is important on a rifle like the SIG Sauer MCX that expects to see high round counts and infrequent depot-level maintenance.
The pressure that moves the carrier rearward also simultaneously pushes the bolt forward into the receiver extension. This forward pressure ensures that the cam pin has enough clearance to rotate freely when the bolt unlocks.
As the MCX’s recoil system is completely contained within the upper receiver there is no need for a buffer tube assembly, according to von Stauffenberg. Instead of the usual screw-in stock adapter, SIG crafted a completely new rear for the MCX: A vertical Picatinny rail to attach their skeletonised stock to the gun, making producing aftermarket parts simple and even easier to configure.
The MCX’s hand guard is a lightweight skeletonized keymod affair. The guards extend about 12in on the barrel for a good length of pull.
Barrel changes are easier than coming-up with a metaphor for something easy. With the hand guard removed, one locks the MCX’s bolt to the rear and unscrew two hex screws on the side of the chamber. Once unscrewed the barrel slides right out.
The barrels are hammer forged and nitrided, offering a significant improvement in barrel life over the standard button- rifled/chrome-lined models of yore.
Because of the risks associated with using .300 BLK ammunition in a 5.56 barrel, SIG Sauer has slotted the bolt-carrier groups so that the 5.56 barrel cannot be assembled with the .300 BLK-marked bolt-carrier group (BCG) and vice versa. The BCG’s markings are visible through the ejection port, providing an important visual indicator showing which barrel is in the weapon.
The SIG SAUER MCX’s fire controls are ambidextrous. Mostly, as the MCX’s bolt release is only available on one side of the gun. The safety selector, available on both sides of the gun, was specifically designed not to impede precision shooting or dig into the shooter’s finger. The rifle’s handsome extended magazine release button is ambidextrous as well, enabling efficient left-handed magazine changes. The charging handle also goes both ways, with latches on both sides of the receiver.
The MCX looks great, the concept behind the operating bits is fantastic, and the execution is spot on.
For more information please see MILITARY TECHNOLOGY #1/2017, available at the show; and frequently check back for more NEWS FROM THE FLOOR.