"The MK2 series, developed by Primary Weapons Systems, and based on the SR25 platform, has been built from the ground up as a short barreled rifle for those requiring the venerable 7.62x51 in a compact package.  Utilizing our proven long stroke piston system, the MK1 series greatly reduces fouling in the action of the weapon making it as reliable as the AK47 that it was designed after. The origins of the MK2 series began with the fascination in the simplicity and reliability of the AK47 combined with a deep-rooted appreciation for the ergonomics of the SR25 platform. Having a significant understanding of the deficiencies in the direct gas impingement operating system found on conventional AR10/SR25-style weapons, PWS developed the MK2 series with the professional operator in mind. Significant product improvements have been made over both the direct impingement operating system and previous offerings of piston-driven operating systems. Our product improvements have addressed reliability and performance issues as well as reduced carrier tilt, cam pin wear and carrier bounce. An innovative hand guard system utilizes a proprietary non-free float system that allows the end user or unit armorer to replace individual rails as needed without removing the barrel, barrel nut or even other rails. This system allows the user to attach numerous picatinny rail mounted devices such as sights, lights, and laser aiming devices. The PWS proprietary operating system utilizes an operating rod that is attached to the carrier and a floating head piston that is attached to the operating rod. The MK2 series is built to be a true combat carbine. With no unnecessary gas adjustments and only one moving assembly, this is the most rugged, simple and versatile piston operating system available."