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SIG MPX: The Ultimate Submachine Gun for Adverse Conditions

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SIG MPX with ROC Marine Corps Special Service Company Operator

The SIG MPX is a submachine gun developed by SIG Sauer in 2013. This weapon features a gas-operated, selective fire system that performs optimally in adverse conditions. The SIG MPX has a unique piston system that reduces recoil, increases accuracy and reliability, and ensures that dirt and water do not enter the chamber, causing stoppages. The weapon also has features that are typically found on assault rifles. The SIG MPX is highly versatile and free to change barrel length and stock configuration while in the field. In this article, we will take a closer look at the design, features, and performance of the SIG MPX.


The SIG MPX is a submachine gun designed with a gas-operated and selective fire system chambered for standard 9×19 mm Parabellum ammunition. Its dimensions and weight resemble the popular Heckler & Koch MP5 submachine gun. Nonetheless, there are notable differences between the two. The SIG MPX boasts a modern design with a modular structure that allows for effortless customization. It is also shorter and lighter than the MP5, enabling easier maneuverability in confined spaces. However, the MP5 has earned a reputation for its exceptional accuracy and reliability, making it a preferred choice among law enforcement and special forces personnel for several decades.

Heckler & Koch MP5 with silencer
Heckler & Koch MP5 submachine gun with silencer attached (Photo: WikiGuns)

The weapon is a scaled-down version of the SIG MCX assault rifle and is the first submachine gun with a fully closed and rotating bolt piston system. The piston system was developed for the SIG MCX assault rifle and is typically associated with assault rifles. The system reduces recoil, increases accuracy and reliability, and ensures that dirt and water do not enter the chamber, causing stoppages.

The SIG MPX has a baseline 165 mm (6.5″) barrel. However, versions of the weapon with different barrel lengths are available. The weapon has an ambidextrous fire mode selector located over the pistol grip, with settings for “safe,” “semi-auto,” and “full-auto.” There are also semi-automatic only versions of the weapon. The charging handle resembles the Armalite AR-15 (M16) assault rifle and is located at the back of the weapon. It does not reciprocate when the weapon is fired and can be charged with either hand.

SIG Sauer MCX rifle
SIG Sauer MCX rifle (Photo: XY)

The SIG MPX has a last-shot bolt hold open and an ambidextrous bolt release button that speeds up the weapon’s reloading. The weapon is fed from 30-round capacity magazines, although smaller magazines are available for civil semi-automatic only versions of the weapon. The SIG MPX has a 3-position telescoping stock, with a version of the weapon also featuring a side-folding buttstock. Some civilian semi-automatic only models have no stock at all or are fitted with a shoulder brace that can act as a buttstock.


The SIG MPX has various features that make it highly versatile and suitable for various environments. The weapon has a full-length Picatinny-type scope rail, and detachable flip-up iron sights are standard. The weapon can also mount various red dot-type sights or laser pointers. The range of effective fire is around 50-75 meters, making the weapon ideal for use in close quarters.

The MPX can be fitted with accessory rails on the foregrip, allowing users to mount various add-on tactical accessories, such as laser pointers, flashlights, etc. The weapon is also highly customizable, allowing users to change the field’s barrel length and stock configuration.


The SIG MPX is a reliable and accurate submachine gun. It has a low recoil, which helps to increase accuracy and ease of control during rapid fire. The fully closed and rotating bolt piston system enhances reliability and reduces malfunctions, making this weapon suitable for military and law enforcement. Additionally, the ability to customize the barrel length and stock configuration makes the SIG MPX versatile for various applications.

The weapon’s ambidextrous fire mode selector and bolt release button are convenient features allowing easier handling and faster reloading times. The charging handle at the back of the weapon can be charged with either hand, adding to the weapon’s versatility. The last shot bolt holds open feature further speeds up the reloading process.

The MPX submachine gun uses a 30-round capacity magazine, which is standard for this type of weapon. However, smaller magazines are available for semi-automatic only versions of the weapon. This makes it easier for civilian shooters to use the weapon in areas with restricted high-capacity magazines.

The SIG MPX prevents dirt and water from entering the chamber and causing stoppages. This feature enhances the weapon’s reliability, particularly in adverse conditions, making it a suitable option for law enforcement and military applications. The weapon’s ability to mount various tactical accessories, such as laser pointers and flashlights, further enhances its performance in tactical situations.


The SIG MPX is a versatile submachine gun in various versions, each designed to serve a particular purpose. The baseline MPX model has a 165 mm (6.5″) barrel, but other variants have different barrel lengths. For example, the MPX-K, with a 140 mm (5.5″) barrel and a side-folding stock, is a more compact option, ideal for easy transportation. The MPX-P is designed for personal defense and has a shorter 127 mm (5″) barrel.

SIG Sauer MPX Copperhead
SIG Sauer MPX Copperhead (Photo: XY)

Furthermore, there are several civilian semi-automatic versions of the weapon. These include the SIG MPX Copperhead, which has a 127 mm (5″) barrel and a no-stock option. The SIG MPX-K Copperhead, with a 140 mm (5.5″) barrel and a side-folding stock, and the SIG MPX-PCC, designed for use in pistol caliber carbine competitions.


The SIG MPX K, also known as the “Kurz,” is a compact version of the gun equipped with a 114 mm (4.5″) barrel. On the other hand, the SIG MPX P is a semi-automatic pistol version with no buttstock and a longer 203 mm (8″) barrel. There are other semi-automatic versions available for civilian customers and various security services.

SIG MPX-K (Photo: XY)


The SIG MPX PSB is another semi-automatic pistol version with a shoulder brace that also serves as a side-folding stock. It comes with a 203 mm (8″) barrel, and the SIG MPX SBR is a pistol version equipped with a collapsible stock, similar to the baseline submachine gun, and a barrel length of either 114 mm (4.5″) or 203 mm (8″).


The SIG MPX SD is a submachine gun with an integral sound suppressor designed primarily for special forces and elite law enforcement units. It shares some conceptual similarities with the Heckler & Koch MP5SD. Lastly, the SIG MPX C is a semi-automatic version that can be distinguished by its exceptionally long barrel. Although it’s called a “carbine,” it’s essentially the baseline MPX submachine gun limited to semi-automatic firing with a 165 mm (6.5″) barrel and an additional 241 mm (9.5″) muzzle attachment permanently welded to the weapon.


SIG MPX PCC is a variant of another derivative of MPX. PCC stands for Pistol Caliber Carbine, which means that it is a carbine-style firearm that fires pistol cartridges, such as 9mm, .40 S&W, and .357 SIG.

The MPX PCC is popular among law enforcement, military personnel, and civilian shooters due to its reliability, accuracy, and modularity. It features a short-stroke gas piston system, which reduces recoil and allows for smoother operation. Additionally, the MPX PCC has a fully ambidextrous design, with controls such as the magazine release and charging handle on both sides of the firearm.


SIG Sauer also offers a range of customization options for the MPX PCC, including various barrel lengths, handguard styles, and stock options. These features make the MPX PCC a versatile and adaptable firearm suitable for various applications, including self-defense, competition shooting, and tactical operations.

It’s also worth noting that the Caracal CMP-9 is a version of the SIG MPX produced under license by Caracal International in the United Arab Emirates.

Legal Considerations

The SIG MPX is a restricted weapon in many countries, including the United States. In the US, the weapon is regulated by the National Firearms Act (NFA) and requires a tax stamp and approval from the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) to own. Additionally, some states have their own regulations regarding the ownership and use of submachine guns.

In countries where the weapon is legal, it is primarily used by military and law enforcement agencies. Civilians may be able to own a semi-automatic-only version of the weapon, depending on their country’s laws and regulations.

Technical specifications

Country of origin:Germany / Switzerland
Manufacturer:SIG Sauer
Entered service:2014
Caliber:9 x 19 mm Parabellum
Weight:2.7 kg
Length (stock extended):610 mm
Length (stock folded):425 mm
Barrel length:165 mm
Muzzle velocity:~ 390 m/s
Cyclic rate of fire:850 rpm
Practical rate of fire:30 – 90 rpm
Magazine capacity:30 rounds
Sighting range:50 meters
Range of effective fire:50 ~ 75 m

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Eric Sof

I'm the active duty law enforcement officer serving in SWAT unit. My hobby's are firearms, skiing, martial arts.

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