The invention relates to a front-end device of an auto-injector (A) for administering a dose of a liquid medicament, comprising of a support sleeve with a first screw thread adapted to engage a housing of a back-end device of the auto-injector (A) to attach the front-end device to the back-end device and an outer sleeve mounted onto a support sleeve of the front-end device by a second screw thread, wherein the front-end device is adapted to receive a syringe with an injection needle and a barrel containing the dose of the medicament and wherein the direction of rotation of the first screw thread is opposite to the direction of rotation of the second screw thread.