A cartridge holder (4) for retaining a cartridge (5) comprising a distal end and a proximal end being spaced apart from one another in the direction of an axis, an interior (50) which is suitable to receive and retain a cartridge (5) in a cartridge retaining section (47B) of the interior (50), and a main part (47) and at least one protrusion (39) which is moveably connected to the main part (47). The protrusion (39) is arranged to define the radial extension of a subsection (10) of the interior (50), wherein the subsection (10) is arranged at an axial position which is further away from the distal end than the cartridge retaining section (47B). Furthermore, the protrusion (39) is arranged to vary the radial extension of the subsection (10) when the protrusion (39) is moved with respect to the main part (47). Moreover, a method for securing a cartridge (5) in a cartridge holder (4) is proposed.