The present invention relates to a drive mechanism for a medicament delivery device, comprising a plunger rod (54) arranged to act on a stopper (28) arranged in a medicament container (16); a compression drive spring (58) operably connected to said plunger rod (54) and capable of applying a force on said plunger rod (54); a spring guide (78) arranged coaxial with, and radially outside, said compression drive spring (58), capable of preventing buckling of said drive spring, wherein said spring guide (78) comprises a resilient force element (86) capable of applying a force on said medicament container (16).