SIG Sauer MPX
SIG Sauer · Submachine Gun · In Production · 2013
Also known as: MPX, SIG MPX, SIG Sauer MPX-SMG
Overview
The SIG Sauer MPX is a gas-operated submachine gun chambered primarily in 9x19mm Parabellum, introduced in 2013 and manufactured in Newington, New Hampshire. Unlike the overwhelming majority of pistol-caliber submachine guns, which rely on simple blowback operation, the MPX uses a short-stroke gas piston system derived from the AR-15/AR-18 lineage, firing from a closed, rotating bolt. This architecture dramatically reduces the reciprocating mass during firing and, combined with the AR-style buffer arrangement housed within the receiver extension, yields exceptionally flat recoil for a 9mm select-fire weapon. The lower receiver mimics AR-15 ergonomics - familiar pistol grip angle, ambidextrous safety selector, bolt catch, and magazine release - making transition from AR platforms intuitive for military and police users. The handguard employs a full-length Picatinny top rail with M-LOK slots, and the quick-change barrel system allows operators to swap between 4.5-inch, 6.5-inch, 8-inch, and 16-inch barrels in the field. Magazines are proprietary translucent polymer boxes holding 20 or 30 rounds, with round count visible to the shooter. The MPX is offered in full-automatic configuration for military and law enforcement customers and in a range of semi-automatic-only pistol, short-barreled rifle, and carbine configurations for the commercial market.
Specifications
| Weight (empty) | 2721 g (96.0 oz) |
| Weight (loaded) | 3062 g (108.0 oz) |
| Overall Length | 660 mm (25.98") |
| Folded Length | 420 mm (16.54") |
| Barrel Length | 203 mm (7.99") |
| Height | 241 mm (9.49") |
| Width | 64 mm (2.52") |
| Action Type | Gas Operated Short Stroke |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 396 m/s (1299 fps) |
| Muzzle Energy | 584 J (431 ft·lbf) |
| Effective Range | 100 m (109 yd) |
| Maximum Range | 200 m (219 yd) |
| Rate of Fire | 850 rpm |
| Barrel Rifling | Right Hand |
| Rifling Twist | 254 mm (10.00") |
| Number of Grooves | 6 |
| Frame Material | Aluminum |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Nitride |
Calibers
- 9x19mm Parabellum · primary · 9mm NATO — also known as 9mm Luger, 9mm NATO, 9x19mm
- .357 SIG — also known as 357 SIG, 9x22mm
- .40 S&W — also known as 40 Smith & Wesson, 10x22mm
Features
- Firing modes: Semi Automatic, Full Automatic
- Feed systems: Detachable Box Magazine, Proprietary Polymer Magazine
- Safety mechanisms: Ambidextrous Manual Safety, Firing Pin Safety, Trigger Safety
- Features: Short Stroke Gas Piston, Closed Bolt Firing, Ambidextrous Controls, Folding Stock, Collapsible Stock, M-Lok Handguard, Free Floating Barrel, User Changeable Barrel, Quick Change Barrel, Ar15 Style Controls, Picatinny Rail, Translucent Polymer Magazine, Select Fire, Suppressor Ready
Variants
- MPX Carbine — Civilian Carbine
- MPX K — Compact
- MPX PSB — Pistol Stabilizing Brace
- MPX Copperhead — Ultra Compact
- MPX SD — Integrally Suppressed
- MPX Tactical — Tactical
Service history
Operators
- British Ministry of Defence Police · adopted 2018 · as MPX
- Royal Thai Police · as MPX
- Saudi Royal Guard · as MPX
- US Law Enforcement (Various) · as MPX
- Indian National Security Guard · as MPX
Production
Production years: 2013-present
In active production. Adopted by law enforcement and military units in the United States, United Kingdom, Thailand, Saudi Arabia, and India. Commercial semi-automatic variants are widely available in the US market.
Origin
Country of origin: United States
Designer: Kevin Brittingham and SIG Sauer engineering team
Notes
The MPX was the first mainstream submachine gun to abandon blowback operation in favor of a gas-piston system, a design choice that required SIG to essentially scale down the AR-15 operating system to a pistol cartridge. Unlike piston-driven rifles, the MPX vents gas very close to the chamber because the 9mm cartridge generates pressure for only a brief moment. Early production guns suffered teething problems with the handguard-retention system and proprietary muzzle devices, which were revised in the MPX Gen 2 in 2017. The Gen 2 also added an AR-15-pattern charging handle, relocated takedown pins, and an improved trigger group. The MPX uses proprietary magazines - it is not compatible with Glock, Colt SMG, or Grease Gun magazines - which has been a consistent point of criticism from users accustomed to interchangeable 9mm feed devices. The MPX Copperhead variant, with a 3.5-inch barrel and PCB pistol brace, is among the shortest select-fire weapons ever mass-produced and was designed for vehicle-borne personal defense.
Background
The MPX was the first mainstream submachine gun to ditch blowback for a short-stroke gas piston, a choice so counterintuitive that the design had to answer one question: why make a 9mm operate like a rifle? The answer came on the range - the gas system and internal buffer tamed recoil so thoroughly that early demonstrators famously fired full-automatic bursts one-handed while the muzzle barely rose, inverting decades of received wisdom about what a 9mm submachine gun could do.