SIG Sauer MCX

MCX
SIG MCX rifle with standard folding
Type	Semi-automatic carbine
Place of origin	United States
Service history
In service	2015–present
Used by	Netherlands Maritime Special Operations Forces U.K. Police CTSFO teams
Production history
Manufacturer	SIG Sauer
Produced	2015–present
Variants	Assault rifle Short-barreled rifle Semi-automatic pistol
Specifications
Weight	2.61 kg (5.8 lb) (229 mm barrel) 2.72 kg (6.0 lb) (406 mm barrel)
Length	730 mm (29 in) stock unfolded (229 mm barrel) 908 mm (35.7 in) stock unfolded (406 mm barrel)
Barrel length	229 mm (9.0 in) 406 mm (16.0 in)
Cartridge	5.56×45mm NATO .300 AAC Blackout 7.62×39mm
Action	Short-stroke gas-operated piston, rotating bolt
Feed system	30-round detachable STANAG box magazine
Sights	Picatinny rail for mounting iron or optical sights

The SIG MCX is a weapon series designed and manufactured by SIG Sauer, featuring a short-stroke gas piston system, carried over from the SIG MPX submachine gun. It is made in both semi-automatic and selective fire configurations. It is available in rifle, short-barreled rifle, and pistol configurations.

Built at SIG's New Hampshire factory, the MCX was "engineered from the ground up to be silenced, light and short" according to a SIG Sauer brochure.

In 2016, SIG recalled some weapons with the first generation bolt carrier group.

The SIG MCX series features a short-stroke gas piston system to reduce recoil and improve the reliability of the weapon; this was based on the design of the earlier SIG MPX. The MCX features a system that allows for conversion between 5.56×45mm NATO, .300 AAC Blackout and 7.62×39mm ammunition, using standard 5.56 mm STANAG magazines for 5.56×45mm NATO and .300 AAC Blackout, and specially designed STANAG-compatible magazines for 7.62×39mm. The MCX is designed to deliver optimal performance with .300 AAC Blackout and an optional suppressor.

The barrel's profile is tapered at the crown to allow the installation of muzzle devices and direct-thread sound suppressors without the use of washers that degrade performance and allows the devices to self-center on installation. The barrel can be changed in a matter of seconds to another length or a different caliber. Additionally the barrels are nitride coated for corrosion resistance. It features hardened steel wear points.

All MCX variants have a forend made of aluminum with a KeyMod system to add accessories. Controls are mostly ambidextrous including the charging handle but not the bolt release. Four types of stocks are available for the MCX carbine.