The invention refers to an auto injector (1) for administering a medicament (M) and to a method for operating it the auto injector (1) comprising: a tubular chassis (2) and a carrier subassembly comprising a tubular carrier (7) slidably arranged in the chassis (2). The carrier (7) contains a syringe (3) a drive spring (8) and a plunger (9) for forwarding load of the drive spring (8) to a stopper (6) arranged in the syringe (3). The syringe (3) is locked for joint axial translation with the carrier (7). A control spring (19) is connectable to the carrier (7) by first interlock means (20 23 24) for needle insertion wherein the whole carrier subassembly is advanced. Second interlock means (11 13 15) are arranged for releasing the drive spring (8) when the carrier (7) has at least almost reached an injection depth thus delivering the medicament (M). The first interlock means (20 23 24) are arranged for decoupling the control spring (8) from the carrier (7) and coupling it to the chassis (2) for advancing it over the needle (4) into a needle safe position.
