Power pack assembly

A power pack assembly for a medicament delivery device comprising:

• a housing extending along a longitudinal axis (L) and having a proximal end near a dose delivery site, a distal end opposite the proximal end, and a track;
• a container carrier unit arranged longitudinally and bi-directionally movable relative to the housing;
• a plunger pusher comprising a transition portion, where the plunger pusher is releasably connected to the container carrier unit;
• a resilient member arranged on the proximal end between the housing and the container carrier unit, the resilient member being configured to exert a pulling force on the container carrier unit towards the proximal end;
• and
• an actuator unit operatively connected to the transition portion,
• wherein the actuator unit moves the plunger pusher axially such that the container carrier unit moves axially distally relative to the housing followed by proximal movement, provided by the resilient member, of the plunger pusher and the container carrier unit until the container carrier unit contacts a proximal stop on the housing whereby the plunger pusher disengages from the container carrier unit and continues to move proximally a further predetermined distance.