A drug delivery device comprising: an outer casing; a primary container disposed in the outer casing and comprising a distal end carrying a dose delivery member, a proximal end carrying a stopper, and an interior chamber extending between the distal and proximal ends, the interior chamber for storing a drug and the stopper movably disposed in the interior chamber for expelling the drug from the dose delivery member at the distal end; a carrier for moving the container relative to the injection drive; a carrier lock for selectively locking the primary container in a ready-to-use mode; an injection drive mechanism disposed in the outer casing and comprising a plunger and a first energy source, the first energy source exerting a first force on the plunger such that upon activation of the injection drive mechanism the first energy source causes the plunger to urge the stopper toward the distal end of the primary container; an injection drive lock for selectively locking the injection drive mechanism in a ready-to-use mode; and a plunger loading mechanism disposed in the outer casing and comprising a second energy source adapted to exert a second force on the primary container to bias the primary container toward the injection drive mechanism, a magnitude of the second force being less than a magnitude of the first force characterised in that upon activation of the plunger loading mechanism, the second energy source of the plunger loading mechanism urges the primary container toward the injection drive mechanism to reduce a distance between the stopper and the plunger, prior to activation of the injection drive mechanism, thereby preventing the plunger from accelerating to a predetermined velocity by the first energy source before it acts on the stopper, wherein the carrier lock resists the second force of the plunger loading mechanism when the device is in a ready-to-use mode to limit movement of the primary container relative to the injection drive mechanism, and wherein the injection drive lock resists the first force when the device is in the ready-to-use mode to limit movement of the plunger relative to the primary container. an outer casing; a primary container disposed in the outer casing and comprising a distal end carrying a dose delivery member, a proximal end carrying a stopper, and an interior chamber extending between the distal and proximal ends, the interior chamber for storing a drug and the stopper movably disposed in the interior chamber for expelling the drug from the dose delivery member at the distal end; a carrier for moving the container relative to the injection drive; a carrier lock for selectively locking the primary container in a ready-to-use mode; an injection drive mechanism disposed in the outer casing and comprising a plunger and a first energy source, the first energy source exerting a first force on the plunger such that upon activation of the injection drive mechanism the first energy source causes the plunger to urge the stopper toward the distal end of the primary container; an injection drive lock for selectively locking the injection drive mechanism in a ready-to-use mode; and a plunger loading mechanism disposed in the outer casing and comprising a second energy source adapted to exert a second force on the primary container to bias the primary container toward the injection drive mechanism, a magnitude of the second force being less than a magnitude of the first force characterised in that upon activation of the plunger loading mechanism, the second energy source of the plunger loading mechanism urges the primary container toward the injection drive mechanism to reduce a distance between the stopper and the plunger, prior to activation of the injection drive mechanism, thereby preventing the plunger from accelerating to a predetermined velocity by the first energy source before it acts on the stopper, wherein the carrier lock resists the second force of the plunger loading mechanism when the device is in a ready-to-use mode to limit movement of the primary container relative to the injection drive mechanism, and wherein the injection drive lock resists the first force when the device is in the ready-to-use mode to limit movement of the plunger relative to the primary container.