The SIG MCX (carbine) is a firearm family designed and manufactured by SIG USA, a subsidiary of the Sig Sauer based in New Hampshire, and made its first appearance to the market in 2015.  This versatile platform has a smooth action that features a short stroke gas piston system with a rotating bolt used in the earlier SIG MPX submachine gun engineered to reduce recoil and improve reliability.  This is the operator’s ultimate sub gun and there are many configurations depending on the purpose, need, or mission.

The SIG MCX is a handy platform with nitride coated barrels to prevent corrosion, and the barrels are available in various lengths of 9.0, 11.5, and 16.0 inches.  The barrels are tapered at the crown to allow attachment of muzzle devices and suppressors without the use of additional hardware that degrade performance and allows attachable devices to self-center upon installation.  

SIG MCX - Wikipedia
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These barrels have hardened steel wear points.  One important feature of the MCX is a system that allows for conversion between 5.56 x 45 mm NATO and .300 AAC Blackout ammunition.  The company was set to include the 7.62 x 39 mm configuration but has removed this caliber from its website.  When chambered for the 5.56 x 40 mm NATO round and effective to 1,650 feet. The muzzle velocity for this round is 3,000 feet/second.

The barrel can be changed rapidly to another length or different caliber.  The SIG MCX holds a standard 30 round detachable STANAG box magazine and fires 800 rounds/minute when using 5.56 x 45mm NATO and .300 AAC Blackout rounds. The MCX was optimized to enhance performance of the .300 AAC Blackout and made an optional suppressor available. 

The fore end of the first-generation SIG MCX variants are made of aluminum with a KeyMod system allowing the addition of various accessories, while the second generation variants have an M-LOK handguard available.  Another excellent feature are the mostly ambidextrous controls that include the charging handle.  

The overall length of the typica MCX is 35.7 inches and reduces down to 29 inches with the stock folded.  There are four types of stocks available for the MCV carbine.  SIG USA designed the MCX upper receiver to be compatible with AR-15 and M16 lower receivers by engineering an adapter.  The overall design and layout of the two rifles are very similar in their working parts.  

SIG MCX VIRTUS Patrol - YouTube
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There are a number of variants of the SIG MCX.  For the US civilian market, the SIG MCX is available with a safe/semi-automatic trigger group.  Foreign and domestic military and law enforcement agencies have the safe/semi-automatic/fully automatic trigger group available.

The SIG MCX is the standard configuration of the rifle with a 16 inch barrel.  The SIG MCX SBR is a short-barreled variant with a 9 inch barrel, more similar in size to the MPX. In the US, the SIG MCX SBR is required a special permit and subject to both state and federal restrictions.  

The SIG MCX Pistol is a pistol configuration with a 9 inch barrel and comes with a pistol stabilizing brace (Sig Sauer SBX) or pistol pivoting contour folding brace (SIG Sauer PCB).  The SIG MCX Low Visibility Assault Weapon (LVAW), also known as the Black Mamba, is a short barreled variant with a suppressor and select-fire mechanism and is available only to military and law enforcement.   

The SIG MCX RATTLER, one of the shortest production rifle-caliber AR pistols ever made, is a short barreled variant designed as a personal defense weapon featuring a 5.5 inch barrel.  It comes from the factory with a Picatinny rail tail to attach either a compact butt stock or a collapsible PCB.  

It is built around an otherwise stock-AR lower receiver.  The RATTLER has an adjustable short-stroke piston-driven gas system known for high reliability and easily manipulated to switch between subsonic and supersonic or hypersonic ammunition.  This weapon’s modular design allows it to be configured with various barrel lengths, buttstocks, and calibers (usually 5.56 and .300 Blackout) in the field with only an Allen wrench.  

Sig MCX Virtus with Eotech xps2 and G33. Letting her bang for the first  time today 👌🏻 : SigSauer
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This incredibly compact variant is threaded 5/8 x 24 for a .30-caliber sound suppressor also manufactured by SIG USA. The SIG SRD762 is the top of the line when it comes to suppressors.  The MCX RATTLER is a sub-variant of the superlative SIG MCX rifle series that can be configured in may different mission-specific combinations.   The MCX Rattler is perhaps a bit quieter with subsonic ammo compared to similar weapons, and the projectiles hit harder compared to the super-sonic ammunition.

Regardless of the need or variant, the SIG MCX system is on the expensive side.  However, the well-developed ergonomics, reliability, and brand reputation are well-worth some of the cost. The SIG MCX is the top choice of many enthusiasts as a primary home defense arm.  Keep in mind when considering a SIG MCX, quality and reliability are second to none.

For fans of the SIG MCX, Sarge has something you will be very fond of to hold on your desk in 2021 ;).


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Written by Nicholas