A mechanism or drive (100) for a weapon is described, which is characterized by only a limited acceleration of the breech (20) and a jerk- and recoil-free operation, thereby reducing the inertia force and the required power and increasing the repetition rate. The reduction of the required power also results in a reduction of braking power in the case of a quick stop. For this purpose, the rotational motion of preferably a motor (50) or the like is converted to a forward or reverse motion of the breech (20) using the Scotch yoke principle. In order to allow rest periods of the breech in the end limit positions, the rod (3) and the yoke (1) are arranged radially and displaceable relative to each other so that the yoke radius changes when the yoke (1) is rotated. A control cam (6) radially guides the rod (3).