An attachable extension can be attached to a firearm adjustment knob comprising an extension rod and a mounting block wherein the extension rod can slide back and forth axially and rotatably within the mounting block. A knob mounted to the extension rod and a spring mounted around the extension rod for biasing the extension rod toward a gas exhaust knob, and a fastener capturing the mounting block to a barrel shroud wherein the knob movably rotates the extension rod axially within the mounting block. The extension rod further comprises a slot fitted over gas exhaust knob. The extension rod can be coupled to the knob by a pin.