Described is a medicament delivery device (1) comprising a plunger (5), a damper plunger (8) coupled to the plunger (5) such that translation of the plunger (5) causes translation of the damper plunger (8), and a chamber (7) filled with a shear thickening fluid (F). Translation of the damper plunger (8) displaces the shear thickening fluid (F) within the chamber (7).