Abstract: A semiautomatic rifle (10) with inertial operation comprises an arming unit (11) and an inertial-loading device (12), where the arming unit (11) has a breechblock (13), there being housed inside the breechblock (13) a firing pin (18), and further has a cocking lever (21) equipped with a corresponding spring (22) and with a kinetic mass (23), as well as with a magazine follower (24) designed to transfer the cartridges (20) supplied by the magazine box (25) of the inertial-loading device (12) to the arming unit (11). The arming unit (11) is functionally associated with the inertial-loading device (12) for loading the cartridges (20) in such a way that it is possible to exploit the inertia associated to the recoil of the rifle when the rifle is fired, both for operation of the arming unit (11) and for feed of the cartridges (20) from the magazine box (25) to the cartridge chamber.