Disclose is an auto-injector with a sub-assembly. The sub-assembly includes a chamber for holding a fluid, the chamber has an exit aperture and an inner surface； and a transfer assembly movably disposed within the chamber. The transfer assembly has an outer surface substantially in contact with the inner surface about its perimeter. The transfer assembly is adapted to transfer fluid into the chamber when the transfer assembly is moved within the chamber. The transfer assembly is adapted to receive a fluid container and transfer fluid from the container into the chamber when the transfer assembly is moved with respect to the chamber. The transfer assembly comprises a hollow fluid transfer needle adapted to engage the fluid container to form a fluid pathway from the container into the chamber through the hollow needle. The transfer assembly has a stopper for blocking fluid movement out of the transfer assembly. The fluid transfer needle is adapted to pierce the stopper to deliver fluid through the stopper into the chamber.
