The SIG MPX is a

gas-operated Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent ...

submachine gun designed and manufactured by

SIG Sauer Several brother companies that design and manufacture firearms use the brand name SIG Sauer . The original company, ''Schweizerische Waggon-Fabrik'' (SWF), later ''Schweizerische Industrie-Gesellschaft'' (SIG), went through several selloffs, ...

, and is primarily chambered in

9×19mm Parabellum The 9×19mm Parabellum (also known as 9mm Parabellum or 9mm Luger or simply 9mm) is a rimless, tapered firearms cartridge. Originally designed by Austrian firearm designer Georg Luger in 1901, it is widely considered the most popular handgun a ...

cartridge. It is a gas-operated firearm featuring a

closed Closed may refer to: Mathematics * Closure (mathematics), a set, along with operations, for which applying those operations on members always results in a member of the set * Closed set, a set which contains all its limit points * Closed interval, ...

rotating Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

bolt. These design features, rare in submachine guns, were chosen to enhance the safety of the user and to have a more reliable firearm. It was designed in 2013 and was released to the general public in 2015. It features the

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 The .357 SIG (designated as the 357 Sig by the SAAMI and 357 SIG by the C.I.P. or 9×22mm in unofficial metric notation) is a bottlenecked rimless centerfire handgun cartridge developed by the Swiss- German firearms manufacturer SIG Sauer, ...

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

SIG MCX The SIG MCX is a family of firearms designed and manufactured by SIG Sauer, produced in both selective fire and semi-automatic only models, and features a short-stroke gas piston system, which is inherited from the earlier SIG MPX submachine gu ...

carbine.

Design details

The standard variant of the MPX comes with an 8.0 inch (20.3 cm) barrel and is chambered in

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). The MPX is also available with different barrel lengths, ranging from 114 to 406mm (4.5- to 16-inch). 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 Short-barreled rifle broadly refers to any rifle with an unusually short barrel. The term carbine describes a production rifle with a reduced barrel length for easier handling in confined spaces. Concern about concealment for illegal purposes ha ...

in most states in the United States.

Features

The standard MPX submachine gun comes with no sights and a full-length Picatinny rail system on the top of the weapon. Gen 2 MPX's come with a flat faced Timney trigger and M-LOK rail. The MPX has a short-stroke gas piston system in order to increase the accuracy of the weapon which operates in

closed bolt A semi or full-automatic firearm which is said to fire from a closed bolt is one where, when ready to fire, a round is in the chamber and the bolt and working parts are forward. When the trigger is pulled, the firing pin or striker fires the ro ...

. 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 A silencer, also known as a sound suppressor, suppressor, or sound moderator, is a muzzle device that reduces the acoustic intensity Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit ...

with greater ease. It features an ambidextrous

selector Selector may refer to: *Selector, electrical or mechanical component, a switch *''Selector'', music scheduling software for radio stations created by Radio Computing Services *Selector, of music, otherwise known as a disc jockey *Selector, a pers ...

switch for fully automatic (law enforcement/military models) and semi-automatic. It also features an ambidextrous bolt catch, and the weapon's exterior appears to be a cross between an

AR-15 An AR-15-style rifle is any lightweight semi-automatic rifle based on the Colt AR-15 design. The original ArmaLite AR-15 is a scaled-down derivative of Eugene Stoner's ArmaLite AR-10 design. The then Fairchild Engine and Airplane Corporation d ...

and a Heckler & Koch MP5A3. The barrel is free-floating and is surrounded by polymer/steel

Picatinny rail The Picatinny rail ( or ), or Pic rail for short, also known as a MIL-STD-1913 rail, 1913 rail or STANAG 2324 rail (cancelled), is a military standard rail interface system that provides a mounting platform for firearm accessories. It was o ...

(later

M-LOK M-LOK, for Modular Lock, is a firearm rail interface system developed and patented by Magpul Industries. The license is free-of-charge, but subject to an approval process. M-LOK allows for direct accessory attachment onto the "negative s ...

) mounts. The

charging handle The cocking handle, also known as charging handle or bolt handle, is a device on a firearm which, when manipulated, results in the bolt (firearms), bolt being pulled to the rear, putting the hammer (firearms), hammer/firing pin, striker into a spri ...

of the weapon is at the back of the weapon, based on the AR-15 design. 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 .

Variants

Selective fire configurations

MPX (Standard variant)

A pistol variant with a three-position collapsible arm support with a stock-like appearance, three-position fire selector if it supports full automatic and an 14” blind pined and welded muzzle brake 16”, 8.0, 6.0 4.5 inch barrel.

MPX-K (Compact variant)

A compact variant with a 114 mm (4.5 inch) barrel.

MPX-SD (Integrally suppressed variant)

A fully suppressed variant with an MP5SD-like integral suppressor, a longer fore-end and an 203 mm (8.0 inch) barrel.

Semi-automatic only configurations

MPX Pistol (Pistol variant)

A semi-automatic only pistol variant with no stock and a 203 mm (8.0 inch) barrel.

MPX PSB (Pistol variant)

A semi-automatic only pistol variant with a SIG SBX pistol stabilizing brace and an 203 mm (8.0 inch) barrel. In the US 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. In early 2017, however, the BATFE withdrew this opinion.

MPX-K (Pistol variant)

A semi automatic only pistol variant with a 114 mm (4.5 inch) barrel.

MPX-C (Carbine variant)

A semi-automatic only carbine variant, featuring a 165 mm (6.5 inch) barrel with a 241 mm (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 A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwanted ...

, but in 2013 the BATFE ruled that the component was a

, 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 - A lawsuit is a proceeding by a party or parties against another in the civil court of law. The archaic term "suit in law" is found in only a small number of laws still in effect today. The term "lawsuit" is used in reference to a civil actio ...

against the BATFE, alleging they had acted in an "arbitrary and capricious manner". In September 2015, Federal Judge Paul Barbadora upheld the BATFE's ruling."Judge favors ATF in Sig lawsuit: It's a silencer"
Guns.com, 25 September 2015 As a result of this SIG has announced a carbine variant with a 406 mm (16 inch) barrel without the muzzle device, designated as the MPX PCC.

Users

References

External links

SIG MPX – SIG Sauer's Official Website

SIG MPX Brochure
{{SIG Sauer firearms 9mm Parabellum submachine guns Modular firearms SIG Sauer submachine guns Weapons and ammunition introduced in 2013