A spindle (242； 414； 542； 642) for driving a bung of a cartridge is provided.The spindle includes a generallycir-cular shaft having an outer surface (560). The generally circular shaftextends from a distal end to a proximal end of said circularshaft. A first helical groove (219； 519； 619) is provided along a firstportion of the outer surface. The first helical groove having afirst pitch. A second helical groove (221； 521； 621) provided along a secondportion of the outer surface of the generally circularshaft. The second helical groove overlapping the first helical groove. Thesecond helical groove having a second pitch.
