The present invention provides an AR variant rifle with a left-sided magazine-release assembly which includes a mag-release catch, a left-sided tool-actuated mag-release actuator, a left-sided actuator cover and a mag-release spring. The actuator is operatively coupled to a mag-release catch and can be actuated by a mag-release tool thereby causing a detachable magazine to be released from a magazine well of the rifle. The actuator cover is configured to be mounted on a left side of the rifle and provides support and substantially shields the mag-release actuator thereby permitting the mag-release actuator to be actuated with any mag-release tool from the left side the lower receiver while preventing the mag-release actuator from being actuated without use of any mag-release tool.