SIG MCX

The SIG MCX is a family of firearms designed and manufactured by SIG Sauer, produced in both selective fire and semi-automatic only models, and features a short-stroke gas piston system, which is inherited from the earlier SIG MPX submachine gun. The MCX is available in rifle, carbine, short-barreled rifle, and pistol configurations (the latter configuration generally conforming to the definition of a compact carbine but for taking a pistol brace rather than a buttstock).
History.
The SIG MCX was first introduced at SHOT Show 2015. The rifle was originally designed by SIG USA, the subsidiary of SIG Sauer based in New Hampshire.
Recall.
In 2016, SIG recalled some of the rifles that had the first-generation bolt carrier group.
Design.
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. SIG Sauer is yet to deliver the 7.62×39mm configuration and has removed the calibre as an option in their official website.
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.
First generation MCX variants have a forend made of aluminum with a KeyMod system to add accessories while second generation MCX variants have an M-LOK handguard. Controls are mostly ambidextrous including the charging handle but not the bolt release. Sig produces four stock configurations are available for the MCX carbine.
SIG designed the upper receiver to be compatible with standard AR-15 and M16 lower receivers with the help of an adapter. The overall layout of the two rifles is similar.
Variants.
SIG MCX.
The SIG MCX is available with a safe/semi-automatic trigger group for the U.S. civilian market, or safe/semi-automatic/fully automatic trigger group for the military and law enforcement agencies.
SIG Sauer offers the rifle in semi-automatic only in three different configurations for the civilian market:
The SIG MCX Low Visibility Assault Weapon (LVAW) is a short-barreled, suppressed, select-fire variant available only to military and law enforcement agencies. It is nicknamed the "Black Mamba".
SIG MCX VIRTUS.
The SIG MCX VIRTUS is the second generation of the SIG MCX series and was introduced in 2017.
SIG MCX RATTLER.
The SIG MCX RATTLER is a short-barreled rifle variant intended to serve as a personal defense weapon, featuring a barrel, and comes with a Picatinny rail tail interface for attaching either a compact buttstock or a folding PCB (pistol contour brace). It is available in 5.56×45mm NATO and .300 AAC Blackout.
Derivatives.
CSASS Program.
The SIG MCX-MR (Mid Range) is SIG Sauer's unsuccessful submission for the United States Army's Compact Semi-Automatic Sniper System (CSASS) program. It is chambered in 7.62×51mm NATO and has selective fire capabilities. It weighs and features a 406 mm (16 in) fluted, 416 stainless steel barrel, with a 1:10 inch twist, which is manufactured by Bartlein Barrels. The gas system features suppressed and unsuppressed settings. Unlike the handguard of the MCX, which slides off after pulling the front pivot pin, the MCX-MR requires popping off two screws first. It features both an M16/AR-15 type charging handle and a left side charging handle. It uses a 20-round magazine and is also compatible with SR-25 lower receivers for use of SR-25 box magazines.