According to Sig Sauer, the SIG MPX is the world’s first submachine gun that operates with a fully closed and locked rotating bolt system. It is a gas-operated short stroke piston system and allows the shooter to change barrel length, caliber and stock configuration in the field to meet mission requirements. Additionally, they claim that it is easily convertible to 9mm NATO, .357SIG or .40S&W. But to me, one of the big advantages is that you are getting AR-style ergonomics.
Tags: Sig Sauer