An injection device comprising: a plunger 42 for expressing medicament from a syringe a delivery mechanism 40 providing a forward biasing force urging the plunger from a rear position to a forward position and a latch 60 releasably holding the plunger against the biasing force, where the latch has an aperture 60 formed by at least two resilient segments 60b, within which a rear end of the plunger is retained in the rear position. To release the plunger from the latch, the device further comprises a trigger 70. The trigger and resilient segments have complementary cam surfaces 76, 67 respectively, which engage when the trigger is moved to outwardly deflect the resilient segments, thereby expanding the aperture to release the plunger. One of the cam surfaces may have a forwardly inward sloped surface, where the other of the cam surfaces may have a generally axially extending ridge or protrusion. The trigger, which may comprise an axially moveable button at the rear of the device and may radially surround the latch, may also have its cam surface on an inner surface of a side wall of the trigger. Also disclosed is a method of modular manufacture and a modular manufacturing system.
