Close quarters combat operators will take decisive advantage from the compact size of the MPX-K variant

SIG Sauer, Inc. − headquartered in Exeter, New Hampshire − is the north-American branch of the Swiss-German arms group known for its pistols, semi-automatic and automatic rifles and carbines, long-range rifles and hunting guns used by countless civilian shooters, private security operators, Police agencies and Military units worldwide. Founded in Switzerland as early as in 1853, the SIG group has always been a manufacturer of extremely high-quality firearms, and the SIG Sauer partnership with the German J.P. Sauer & Sohn GmbH company was founded in the 1970s to start the manufacture of the P-220 pistol, the foreruner of the current SIG-Sauer pistols line, which is highly appreciated and a top seller between professionals worldwide. The arms and defense-related branch of SIG, formerly known as SIG Arms A.G., was absorbed in the early 2000s by the L&O Holding A.G. corporation, funded by the German investors Michael Lüke and Thomas Ortmeier, and now the SIG Sauer brand lives under the umbrella of the SAN - Swiss Arms A.G. company.

The MPX-P subcompact variant will be available as a stockless, concealable machine-pistol for VIP protection duties

For 2013, SIG Sauer scores another hit by introducing its highly-anticipated new sub-machinegun system at the Las Vegas SHOT Show. Dubbed the MPX, SIG Sauerʼs new sub-machinegun totally departs from whatever else there is on the market due to its unique technical layout: it is in fact the world’s first submachine gun that operates with a fully closed and locked rotating bolt system, employing SIGʼs gas-operated short stroke piston/push-rod system for unequaled reliability in the field, even under the most adverse conditions, and greatly enhancing operator's safety. Furthermore, the SIG Sauer MPX embodies the concept of modularity under many points of view, including the quick-change components that allow the user to convert any MPX variant from the factory standard 9x19mm chambering to .40-Smith & Wesson and even .357-SIG for maximum operational versatility. Magazine capacity remains 30 rounds for all models; clear plastic magazines, with polymer follower and metal spring, are manufactured in the U.S. by Lancer Systems L/P, well known for its L5-AWM polymer magazines for AR-15 type rifles and carbines.

The MPX-SD variant will feature an integrally-silenced barrel for covert operations

The SIG Sauer MPX sub-machinegun system comprises four select-fire, Mil/LE-only models and a civilian-legal, semi-automatic carbine.

The standard variant, dubbed simply the MPX, sports a 6.½” barrel and either a telescoping or side-folding stock, which bring the overall lenght respectively to 23 or 24 inches wen open. An even shorter variant, named the MPX-K, is merely 21 or 22-inch long with the stock extended − be it the folding or telescoping version − and comes with a 4.5” barrel. The MPX-P, conceived for special applications (es. VIP protection) is akin to the standard MPX, with its 6.½” barrel, but features no stock, bringing the overall lenght to merely 13 inches. The final select-fire version, dubbed the MPX-SD, has a 6.½-inch barrel entirely wrapped in an integral silencer, which brings the overall lenght to a maximum of 33” with stock open but ensures maximum quiet when shooting, for covert applications

The MPX-C semi-automatic carbine is a civilian-legal, 16”-BBL version of the MPX sub-machinegun, conceived for 3-Gun and IPSC competition

Last but not least, the MPX-C semiautomatic-only carbine, conceived for the civilian market, features a collapsible buttstock and a 16” barrel comprising a massive muzzle compensator for competition purposes. 

All MPX variants are built out of machined aluminium, come with a MIL-STD-1913 “Picatinny” rail system on top and an aluminum rail-adaptable handguard for tactical sights and accessories, and sport the same controls configuration − cocking handle, safety/fire selector switch, magazine release catch, hold-open device − as the M16/M4 family of rifles and carbines, of which SIG Sauer itself has been manufacturing variants of for some time now, in order to make it easier for operators trained on AR-15 -based firearms to get accustomed with the platform and thus minimize the time and effort required to re-train the personnel with the new weapon.