The MR A4 SBR is the pinnacle of that evolution, providing unmatched capability and uncompromising durability. You can simply run this rifle harder and longer without a degradation of accuracy or reliability. The entire design has been strengthened and improved. Its short stroke gas piston operating system does not impart hot carbon fouling back into the action, allowing the weapon to run longer, with less maintenance and with less wear on internal components. Its adjustable gas regulator allows the operator to tune the action specifically for suppressed or unsuppressed deployment. The MR A4 SBR is the top-tier solution for those who demand performance and reliability over everything else.