A subassembly (100) of a medicament delivery device (102), the subassembly (100) comprising a housing (104) configured to contain a medicament container structure (250) from which medicament is expelled during use of the medicament delivery device (102), the housing (104) having a proximal end (106) and a distal end (108), and a drive assembly (110) comprising a plunger rod (124) at a proximal end (120) of the drive assembly (110), the plunger rod (124) being configured to, upon activation, apply an activating force on the medicament container structure (250) for expelling the medicament from the medicament delivery device (102), wherein the proximal end (106) of the housing (104) comprises an opening (112), and the distal end (108) comprises a sealable portion (114), wherein the drive assembly (110) is insertable into the housing (104) at the proximal end (106) to form the subassembly (100).