A method of providing a sterilized cartridge assembly for use with an injection system, the method comprising: (a) providing a sealed ampule containing a pharmaceutical product; the ampule having a pierceable diaphragm sealing the ampule at a distal end thereof; an end cap holding the diaphragm in place to define a distal portion of the ampule, and a neck-down portion of the ampule proximally adjacent the distal portion; the neck-down portion having a shoulder adjacent the distal portion of the ampule and the end cap having an outer surface extending proximally from the distal end toward the shoulder; and forming an annular groove on the outer surface of the end cap; (b) providing a hub comprising a proximal portion defining a cavity configured to receive and engage the distal portion of the ampule, the cavity including a radially inwardly facing annular bead for mating with and frictionally engaging the annular groove on the outer surface of the end cap defining said distal portion of the ampule distal of the shoulder and limiting axial movement in both directions between the hub and the ampule in a static initial inactivated position of the cartridge assembly, and a plastic piercing member for piercing the diaphragm; (c) connecting the ampule to the hub so that the bead frictionally engages the groove to define the static initial inactivated position of the cartridge assembly in which the hub is mounted on the ampule, with the ampule engaged and at rest due to the frictional engagement of the bead and the groove, wherein the piercing member contacts the diaphragm and applies a force that pushes a center of the diaphragm out of its resting plane so that the diaphragm is in a proximally flexed position, without causing the piercing member to pierce the diaphragm of the ampule, so as to define a preloaded condition of the diaphragm and thus the cartridge assembly and then; (d) autoclaving the cartridge assembly while the cartridge assembly is in the preloaded condition without causing the piercing member to pierce the diaphragm of the ampule. (a) providing a sealed ampule containing a pharmaceutical product; the ampule having a pierceable diaphragm sealing the ampule at a distal end thereof; an end cap holding the diaphragm in place to define a distal portion of the ampule, and a neck-down portion of the ampule proximally adjacent the distal portion; the neck-down portion having a shoulder adjacent the distal portion of the ampule and the end cap having an outer surface extending proximally from the distal end toward the shoulder; and forming an annular groove on the outer surface of the end cap; (b) providing a hub comprising a proximal portion defining a cavity configured to receive and engage the distal portion of the ampule, the cavity including a radially inwardly facing annular bead for mating with and frictionally engaging the annular groove on the outer surface of the end cap defining said distal portion of the ampule distal of the shoulder and limiting axial movement in both directions between the hub and the ampule in a static initial inactivated position of the cartridge assembly, and a plastic piercing member for piercing the diaphragm; (c) connecting the ampule to the hub so that the bead frictionally engages the groove to define the static initial inactivated position of the cartridge assembly in which the hub is mounted on the ampule, with the ampule engaged and at rest due to the frictional engagement of the bead and the groove, wherein the piercing member contacts the diaphragm and applies a force that pushes a center of the diaphragm out of its resting plane so that the diaphragm is in a proximally flexed position, without causing the piercing member to pierce the diaphragm of the ampule, so as to define a preloaded condition of the diaphragm and thus the cartridge assembly and then; (d) autoclaving the cartridge assembly while the cartridge assembly is in the preloaded condition without causing the piercing member to pierce the diaphragm of the ampule.