An auto injector (4) for administering injection of a medicament from a cartridge (700) containing the medicament, the auto injector comprising: a cartridge receiver (300) with a cartridge receiver compartment (302) configured to receive a cartridge assembly (600) with at least one cartridge retention member (808) when inserted through a cartridge receiver opening (302) along a longitudinal axis； and an ejector (200) configured to support the cartridge assembly (600) by being suspended to move along the longitudinal direction and being spring-loaded in the direction opposite of the receiving direction. The cartridge receiver compartment (302) has a first section (310), at a first distance from the cartridge receiver opening (301), with inwardly extending first guide members (312) that extends over first guide member angles (314) and are spaced apart to form a passage (316) at passage angles (318) between the inward first guide members (312)； wherein the inward first guide members (312) form a first bore (320) accepting the cartridge assembly (600) when inserted through the cartridge receiver opening (301). The cartridge receiver compartment (302) has a second section (330) with an annular shape, at a second distance from the cartridge receiver opening (301), and with second guide members (322) with first faces (324) that are inclined about a radial axis to the longitudinal axis and angularly arranged to extend at least partly over the passage angles (318) and the first guide member angles (314).
