SIG MCX
A modular gas-piston rifle family adopted as the U.S. Army M7.
The SIG MCX is a family of rifles designed and manufactured by SIG Sauer, produced in both selective fire assault rifle configuration and semi-automatic only models. It features a short-stroke gas piston system inherited from the earlier SIG MPX submachine gun. The MCX served as the basis for SIG Sauer's NGSW-R submission, the SIG MCX-SPEAR, which was formally adopted as the M7 rifle by the U.S. Army in 2022.
Quick Facts
- Origin
- United States
- Is Ranged
- Yes
- Service
- 2015–present
- Design Date
- 2013
- Production Date
- 2015–2017 (MCX Gen I) / 2017–2022 (MCX VIRTUS) / 2022–present (MCX-SPEAR LT)
- Manufacturer
- SIG Sauer
- Unit Cost
- MCX VIRTUS Patrol: MSRP US$2,233 / MCX VIRTUS SBR: MSRP US$2,233 / MCX VIRTUS Pistol: MSRP US$2,235
- Weight
- 2.61 kg (229 mm barrel) / 2.72 kg (292 mm barrel) / 3.6 kg (406 mm barrel)
- Length
- 730 mm stock unfolded (229 mm barrel) / 908 mm stock unfolded (406 mm barrel)
- Part Length
- 229 mm / 292 mm / 406 mm
- Cartridge
- 5.56×45mm NATO / .300 AAC Blackout / 7.62×39mm
- Action
- Gas-operated short-stroke piston system, rotating bolt
Facts from the source article.
Lore & Background
The SIG MCX was introduced at SHOT Show 2015, originally designed by SIG USA in New Hampshire. In 2016, SIG recalled some first-generation rifles due to issues with the bolt carrier group. The MCX has been used by various SWAT teams and militaries, including the Ukrainian Armed Forces during the Russian Invasion of Ukraine. An MCX was used in the 2016 Orlando nightclub shooting, the deadliest mass shooting in U.S. history until exceeded by the 2017 Las Vegas shooting.
The MCX series features a short-stroke gas piston with dual recoil spring system, based on the SIG MPX. It enables conversion between 5.56×45mm NATO, .300 AAC Blackout, and 7.62×39mm ammunition, using standard STANAG magazines for the first two calibers and specially designed STANAG-compatible magazines for 7.62×39mm. The barrel can be changed in seconds to another length or caliber, and is nitride coated for corrosion resistance. First generation variants have a KeyMod handguard; second generation use M-LOK. Controls are mostly ambidextrous, and the upper receiver is compatible with standard AR-15 and M16 lower receivers with an adapter.
An integrally suppressed upper receiver group based on the MCX was selected by USSOCOM for the SURG contract in July 2018. The MCX LVAW is a short-barreled, suppressed, select-fire variant available only to military and law enforcement. The MCX Rattler, a personal defense weapon with a 140 mm barrel, was selected as the winner of SOCOM's Commercial Personal Defense Weapon contract in May 2022.
Reader's Guide
The SIG MCX represents a significant evolution in gas-piston rifle design, combining the reliability of a short-stroke system with modularity across multiple calibers and barrel lengths. Its adoption as the U.S. Army M7 rifle in 2022 marks a historic shift from the M16/M4 lineage to a new platform chambered in .277 Fury. The MCX's design influenced the MCX-SPEAR, which won the NGSW-R competition. The rifle's ability to quickly swap barrels and calibers, along with its compatibility with AR-15 lower receivers via an adapter, made it popular among both civilian and military users. The MCX has seen combat use with Ukrainian forces and has been adopted by numerous law enforcement and special operations units worldwide, including USSOCOM for suppressed upper receiver groups and personal defense weapons. Its three generations—original, Virtus, and SPEAR LT—show continuous refinement in handguard design, bolt catch, and suppressor compatibility.
More in Assault Rifles, Part 3 1-24
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