Applicant has disclosed a handheld tool and related method for cleaning and lubricating: the entire star chamber in a firearm (e.g., AR-15 and M-14 rifles), including the top lands, bottom lands, and canted faces of the locking lugs forming a star inlet to the chamber in a rifle; and the remaining headspace of the firearm. One tool embodiment comprises: a paddle grip; a midsection shank; and a generally T-shaped foam swab affixed over an end portion of the shank, wherein the swab has two wings and a stem. The wings are designed to fit, simultaneously or contemporaneously, between and against opposing faces of different pairs of successive locking lugs and against bottom lands of those different pairs. Afterwards, the swab can be pushed through the star inlet to clean the chamber portion behind the inlet, including the backside of the inlet.