The SIG MCX family has undergone three generations of modifications.
SIG MCX (Gen I) 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. though it is really a compact carbine rifle, as it fires an intermediate round. 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 (Gen II) The SIG MCX VIRTUS is the second generation of the SIG MCX series and was introduced in 2017. • The
SIG MCX VIRTUS Patrol is the standard configuration rifle that features a 406 mm (16 in) barrel, a 1:7 inch twist, a custom SIG Matchlite Duo Trigger for improved accuracy, a folding and collapsing 5-position stock, four handguard lengths to choose from, interchangeable barrels and a special internal recoil system. • The
SIG MCX VIRTUS SBR is the short-barreled rifle configuration of the MCX VIRTUS. It features a 292 mm (11.5 in) barrel for the 5.56×45mm NATO caliber, and a 140 mm (5.5 in) barrel and 229 mm (9 in) barrel for the .300 AAC Blackout caliber. • The
SIG MCX VIRTUS Pistol is the pistol configuration of the MCX VIRTUS which features an SBX stabilizer brace. It features an 292 mm (11.5 in) barrel for the 5.56×45mm NATO caliber, and a 229 mm (9 in) barrel for the .300 AAC Blackout caliber.
SIG MCX-SPEAR LT (Gen III) The SIG MCX-SPEAR LT is the third generation of the SIG MCX, introduced in 2022. With the release of the MCX-SPEAR LT, SIG also designed a new, padded, side-folding stock with an FDE finish option to match the rifles, which civilian versions of the rifle variant are sold with. While the civilian version is referred to as the "MCX-SPEAR LT", referencing the SPEAR from which it derives many of its improvements over the MCX Virtus line, SIG Sauer refers to the military versions as simply the "MCX LT" or "MCX Lightweight". The defining features of the MCX-SPEAR LT are a lightened handguard and barrel design (borrowed from the MCX-SPEAR), an ambidextrous bolt catch and release, a proprietary SL muzzle device to allow for the use of SIG SAUER's quick detaching SLX and SLH suppressors, a custom 28-round AR-pattern magazines when chambered in 7.62×39mm cartridge, and a
coyote brown coating (black options are still available for purchase). The MCX-SPEAR LT is available in
5.56×45mm NATO,
.300 Blackout and
7.62×39mm calibers. The civilian model features or barrel and a
Picatinny rail tail interface for attaching either a
buttstock or a pistol brace. The military model features both of these options, with the addition of and barrels, as well as a custom two-stage match grade select-fire trigger group.
SIG MCX RATTLER The SIG MCX RATTLER is a
short-barreled rifle variant chambered in either
.300 AAC Blackout and
5.56×45mm NATO. It is 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). In February 2018,
USSOCOM ordered upper receiver group conversion kits for the MCX Rattler in .300BLK for evaluation. The MCX Rattler was later selected as the winner of SOCOM's Commercial Personal Defense Weapon (CPDW) contract in May 2022 and suppressed MCX Rattlers will be ordered in 5.56 and .300BLK. The
SIG MCX Rattler LT is a variant that incorporates the design features of the MCX-SPEAR LT. ==Derivatives==