Garand Thumb checks out the Sig MPX SBR if it is something he can use in the situations when an SBR is needed. The SIG MPX is a gas-operated submachine gun designed and manufactured by SIG Sauer, primarily chambered in 9x19mm Parabellum. It features a closed, rotating bolt system for enhanced safety and reliability, a design choice uncommon in submachine guns. Designed in 2013 and released in 2015, the MPX utilizes the SIG Sauer short-stroke push-rod gas system to reduce recoil and improve reliability. While the second-generation MPX was intended to allow conversion to .357 SIG or .40 S&W, first-party conversion kits have never been made available.