The invention relates to a front end (1) for an auto-injector, the front end (1) comprising a syringe (2) with an injection needle (3) and a stopper (5), wherein the syringe (2) is slidably arranged within a syringe retainer (26), wherein an outer sleeve (7) for preventing access to the needle (3) is removably arrangeable over the syringe retainer (26), wherein the syringe retainer (26) comprises a screw thread (27) for connecting it to a correspondent screw thread of a mounting (39) of a re-usable auto-injector back end (36) comprising a drive means for advancing the syringe (5) and needle (6) in a proximal direction (P) for needle insertion and for advancing the stopper (7) within the syringe (5) for injection, wherein a resilient locking barb (37) is arranged to rotationally lock the syringe retainer (26) to the mounting (39) in an unscrewing direction when the front end (1) is screwed to the re-usable back end (36) and when the outer sleeve (7) is removed, wherein the outer sleeve (7) is arranged to unlock the resilient locking barb (37) when arranged over the syringe retainer (26).
