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Type Submachine gun
Place of origin Germany, United States
Production history
Manufacturer SIG Sauer
Produced 2013
Variants See Variants
Weight 2.7 kg (6.1 lbs)
  • 425 mm (16.7 in), stock folded
  • 610 mm (24.0 in), stock extended
Barrel length 114 mm (4.5 in)
165 mm (6.5 in)
203 mm (8 in)

Cartridge 9×19mm Parabellum
Action Short-stroke gas-operated, closed bolt
Rate of fire 850 RPM
Maximum firing range 3700 M
Feed system 10-, 20- or 30-round detachable box magazine

The SIG MPX is a gas-operated submachine gun designed and manufactured by SIG Sauer, and is primarily chambered in 9×19mm Parabellum cartridge. It is gas-operated firearm, featuring a closed, rotating bolt.[1] These design features, rare in submachine guns, were chosen to enhance the safety of the user and to have a more reliable firearm.[2] It was designed in 2013 and was released to the general public in 2015.[3] It features the SIG Sauer short stroke push-rod gas system to reduce the recoil and improve the reliability of the weapon.

The MPX, in its second generation, features a system that would allow for conversion from 9mm to .357 SIG or .40 S&W, however, since its inception, first party conversion kits have not been made available for either of the two production generations of the submachine gun.[4]

SIG Sauer also used the same gas piston system to develop the SIG Sauer MCX carbine.

Design details[edit]

The standard variant of the MPX comes with an 8.0 inch (20.3 cm) barrel and is chambered in 9×19mm Parabellum cartridge. It comes with a collapsible stock and a free-floating rail. It has a cyclic rate of fire of 850 rounds per minute (RPM).[5][6]

The MPX is also available with different barrel lengths, ranging from 4.5- to 16-inch.[7] The MPX submachine gun is only available for military and law enforcement use, while a semi-automatic only version is also available for the civilian market.

The semi-automatic version of the weapon can be registered as a Short-Barreled Rifle in most states in the United States.[4]


The standard MPX submachine gun comes with a rear and front flip-up sight that is attached to the integrated rail system on the top of the weapon. One available modification is a SIG reflex sight mounted to the rail instead of the flip-up sights.

The MPX has a gas short stroke piston system in order to increase the accuracy of the weapon which operates in closed bolt.[1] It is designed in this way to prevent water or dirt from entering the chamber and causing malfunctions as well as to use a suppressor with greater ease.[8] It features an ambidextrous selector switch for fully automatic (law enforcement/military models) and semi-automatic. It also features an ambidextrous bolt catch, and the weapons exterior appears to be a cross between an AR-15 and a Heckler & Koch MP5A3. The barrel is free-floating and is surrounded by Polymer/Steel Rail mounts.

The charging handle of the weapon is based on the AR-15 design at the back of the weapon. This is to ensure that cocking the weapon does not interfere with any optics mounted onto the Picatinny rail. The weapon's rails are made out of cast steel and the standard weapon overall weighs 2.1 kg.


Selective fire configurations[edit]


MPX (Standard variant)[edit]

A standard submachine gun variant with a folding stock or a three-position collapsible stock, three-position fire selector and an 8.0 inch barrel.[9]

MPX-K (Compact variant)[edit]

A compact variant with a 4.5 inch barrel.

MPX-SD (Integrally suppressed variant)[edit]

A fully suppressed variant with an MP5SD-like integral suppressor, a longer fore-end and an 8.0 inch barrel.

Semi-automatic only configurations[edit]

MPX Pistol (Pistol variant)[edit]

A semi-automatic only pistol variant with no stock and an 8.0 inch barrel.

MPX PSB (Pistol variant)[edit]

A semi-automatic only pistol variant with a SIG SBX pistol stabilizing brace and an 8.0 inch barrel. In 2015, the BATFE warned users of weapons using SIG stabilizing braces that shouldering a weapon fitted with a brace constituted the making of a Title II NFA weapon, reversing a prior ruling that it did not.[10] In early 2017, however, the BATFE withdrew this opinion, once again making stabilizing braces an attractive solution. [11]

MPX-C (Carbine variant)[edit]

A semi-automatic only carbine variant, featuring a 6.5 inch barrel with a 9.5 inch muzzle device permanently welded to it, which is actually a modified version of the baffle core of the integrally suppressed variant. SIG contended that this device was a muzzle brake, but in 2013 the BATFE ruled that the component was a suppressor, and classified the MPX-C as possessing an integral suppressor and thus as a Title II NFA weapon. The BATFE rejected an appeal against this ruling in February 2014; SIG responded by filing a civil lawsuit against the BATFE,[12] alleging they had acted in an "arbitrary and capricious manner". In September 2015, Federal Judge Paul Barbadora upheld the BATFE's ruling.[13]

As a result of this SIG has announced carbine variant with a 16 inch barrel without the muzzle device, designated as the MPX Carbine.[2]



  1. ^ a b Ayoob, Massad (14 May 2014). Gun Digest Book of SIG-Sauer. Iola, Wisconsin: F+W Media. ISBN 978-1-4402-3920-5.
  2. ^ a b Staff (January 14, 2016). "SIG Sauer Announces MPX 9 mm Semi-automatic Carbine". by American Rifleman.
  3. ^ Staff (April 11, 2015). "Long-Awaited SIG MPX in 9 mm Now Shipping". by American Rifleman.
  4. ^ a b Harrison, Iain (2015). "SIG SAUER MPX – Next-Gen Sub Gun". 3 (21). Recoil.
  5. ^ MPX, SIG. "SIG MPX Brochure (PDF)" (PDF).
  6. ^ "Modern Firearms - SIG-Sauer MPX submachine gun (USA)". Retrieved 2017-08-27.
  7. ^ Mann, Richard Allen; Lee, Jerry (20 November 2013). The Gun Digest Book of Modern Gun Values: The Shooter's Guide to Guns 1900-Present. Iola, Wisconsin: F+W Media. p. 206. ISBN 978-1-4402-3752-2.
  8. ^ Sweeney, Patrick (18 January 2016). Gun Digest Book of Suppressors. Iola, Wisconsin: "F+W Media, Inc.". p. 139. ISBN 978-1-4402-4532-9.
  9. ^ Crane, David (May 24, 2014). "SIG SAUER MPX KeyMod Multi-Cal Machine Pistol/Mini Submachine Gun (SMG)/PDW (Personal Defense Weapon) with Silencer/Sound Suppressor at NDIA SOFIC 2014". Defense Review.
  10. ^ The Rise And Fall Of The SB-15 ‘Sig Brace’ Grand View Outdoors. March 24, 2015.
  11. ^ [1]
  12. ^ "ATF Rules Against SIG MPX", The Outdoor Wire, 14 April 2014
  13. ^ "Judge favors ATF in Sig lawsuit: It's a silencer",, 25 September 2015
  14. ^ "KomChadLuek 7 Jan 2018".

External links[edit]