Editor’s Note: The Sig MPX-K utilizes a 4.5-inch carbon steel barrel to help bring the already maneuverable MPX into an even lighter, handier package. Additionally, the MPX-K features a reliable and durable gas-piston system to help that helps reduce recoil and aids in suppression. The MPX also has fully ambidextrous AR-style controls, a Timney flat-face trigger, and boasts modularity that allows users to easily change handguards and barrel lengths.