The MR556 A4 represents the peak of that evolution, offering unmatched capability and rugged durability. You can run this rifle harder and longer without sacrificing accuracy or reliability. The entire design has been reinforced and refined. Its short stroke gas piston operating system prevents hot carbon fouling from reaching the action, allowing the weapon to operate longer with less maintenance and reduced wear on internal parts. Its adjustable gas regulator enables the operator to fine-tune the action for either suppressed or unsuppressed use. The MR556 A4 is the top choice for those who prioritize performance and dependability above all else.