The SIG MPX redefines the submachine gun category with a new level of operator safety, in-field adaptability and proven reliability in the harshest environments. The MPX features a fully locked and closed rotating bolt system, which provides maximum safety in case of bullet or water obstruction in the bore. SIG's short-stroke piston system reduces recoil and fouling. The bolt is held open on the last round fired. The monolithic upper receiver features an integral M1913 rail at 12 o'clock and a free-floating barrel. The MPX has a familiar, AR-style ambidextrous selector and magazine release, making the transition easy for users who've been shooting a traditional AR. The magwell is flared and beveled for easy reloading. The SB15 Stabilizing Brace provides improved accuracy and reduced recoil for pistol models. The unique design uses the forearm to provide a natural and comfortable rest for shooters of all sizes and physical ability. The barrel, stock, and handguard are all interchangeable for quick configuration changes with a bevvy of options available.