The invention relates to a chamber lock (1) for a firearm, having an outer, tubular lock housing (2) and a pushbutton firing pin spring tensioning device (4) provided therein, wherein the pushbutton firing pin spring tensioning device (4) comprises a latching device (6) acting directly or indirectly in the interior of the lock housing (2) positioned between the lock housing (2) on one side and a clamping sleeve (10) for tensioning the firing pin spring (7) on the other side, the latching device being configured such that the firing pin spring (7) can be tensioned in a repeating manner upon pushing the pushbutton (13) of the pushbutton firing pin spring tensioning device (4) once, and subsequently can be maintained in the tensioned state by means of the latching device (6), and that the firing pin spring (7) can be released upon removing the latching effect of the latching device (6) upon a subsequent pushing of the pushbutton (13) of the pushbutton firing pin spring tensioning device (4).