Equilibrium-adjustment theory, first articulated by Professor Orin Kerr for Fourth Amendment cases, holds promise for rationalizing Second Amendment doctrine going forward. Like the Fourth Amendment, the Second Amendment suggests an initial equilibrium—or actually, multiple equilibria—between government power to possess, use, and control the implements of violence and private power to do the same. And, like Fourth Amendment doctrine, Second Amendment doctrine must contend with both technological and societal change. These changes—e.g., more deadly and accurate weapons, more public acceptance of concealed carry—can upset whatever initial balance of gun rights and regulation there may have been in the initial state. Although this Essay recognizes factors that make Second Amendment equilibrium-adjustment distinctive and challenging, the theory may nonetheless allow courts and scholars to get some purchase on the problem of change in Second Amendment adjudication and provide a vocabulary to explain the objectives of the emerging doctrine for the right to keep and bear arms.