A medical delivery system comprising: - a container adapted to contain a medicament in a chamber defined by the container and a slidably arranged piston which is movable in a distal direction towards an outlet so as to reduce the volume of the chamber and expel the medicament through the outlet; - a dosing assembly adapted to be fastened to the container and comprising: - an actuator for advancing the piston in the distal direction, - a drive mechanism for advancing the actuator in the distal direction, and - a coupling mechanism movable between a distal position wherein movement of the drive mechanism in the distal direction is not transferred to the actuator, and a proximal position wherein movement of the drive mechanism in the distal direction is transferred to the actuator whereby the piston is moved in the distal direction and the medicament is expelled; and - wherein one of the container and the dosing assembly defines one or more radially extending fastening projections each of which during fastening of the container to the dosing assembly engages a corresponding radially extending fastening groove of the other one of the dosing assembly and the container, wherein the one or more radially extending fastening projection(s) and the corresponding fastening groove(s) are so configured that the fastening procedure of the container to the dosing assembly includes an initial relative axial movement followed by a relative rotational locking movement; - characterized in that one of the container and the coupling mechanism defines one or more radially extending retaining projections each of which during fastening of the container to the dosing assembly engages a corresponding radially extending retaining groove of the other one of the coupling mechanism and the container, whereby the coupling mechanism is moved from the distal position to the proximal position. - a container adapted to contain a medicament in a chamber defined by the container and a slidably arranged piston which is movable in a distal direction towards an outlet so as to reduce the volume of the chamber and expel the medicament through the outlet; - a dosing assembly adapted to be fastened to the container and comprising: - an actuator for advancing the piston in the distal direction, - a drive mechanism for advancing the actuator in the distal direction, and - a coupling mechanism movable between a distal position wherein movement of the drive mechanism in the distal direction is not transferred to the actuator, and a proximal position wherein movement of the drive mechanism in the distal direction is transferred to the actuator whereby the piston is moved in the distal direction and the medicament is expelled; and - an actuator for advancing the piston in the distal direction, - a drive mechanism for advancing the actuator in the distal direction, and - a coupling mechanism movable between a distal position wherein movement of the drive mechanism in the distal direction is not transferred to the actuator, and a proximal position wherein movement of the drive mechanism in the distal direction is transferred to the actuator whereby the piston is moved in the distal direction and the medicament is expelled; and - wherein one of the container and the dosing assembly defines one or more radially extending fastening projections each of which during fastening of the container to the dosing assembly engages a corresponding radially extending fastening groove of the other one of the dosing assembly and the container, wherein the one or more radially extending fastening projection(s) and the corresponding fastening groove(s) are so configured that the fastening procedure of the container to the dosing assembly includes an initial relative axial movement followed by a relative rotational locking movement; - characterized in that one of the container and the coupling mechanism defines one or more radially extending retaining projections each of which during fastening of the container to the dosing assembly engages a corresponding radially extending retaining groove of the other one of the coupling mechanism and the container, whereby the coupling mechanism is moved from the distal position to the proximal position.