An autoinjector 200 comprising: a plunger assembly 213 having a delivery spring 217 acting between a spring housing 210 and a plunger with a first release mechanism 218 releasably securing the plunger to the spring housing 210； an insertion spring 219 acting between a housing and plunger assembly 213； a second release mechanism 204 for releasing the plunger assembly 213 from the housing enabling insertion spring 219 to move plunger assembly 213 through the housing together with a collar 206； a stop for blocking collar 206 movement beyond a point in the housing； a third release mechanism for releasing the plunger assembly 213 from the collar 206 upon its engagement with the stop to allow plunger assembly 213 to continue progressing through the housing. On contact between the plunger assembly 213 and a bung of the syringe, the first release mechanism 218 releases the plunger from the spring housing 210, causing delivery spring 217 to drive spring housing 210 and plunger separation and to apply a delivery force to the bung. Autoinjector 200 further comprises a mechanism for latching spring housing 210 at a forward position and preventing rearward spring housing 210 movement after releasing the plunger from spring-housing 210.
