An autoinjector includes: an insertion spring between a housing and plunger assembly； a syringe driver； a second release mechanism releasing the plunger assembly from the housing, causing the insertion spring to move the plunger assembly through the housing with a syringe driver； a stop limiting movement of the syringe driver in the housing； and a third release mechanism releasing the plunger assembly from the syringe driver upon engagement with the stop, allowing the plunger assembly to continue through the housing. The first release mechanism releases the plunger from the delivery spring housing upon contact between the plunger assembly and a bung, causing the delivery spring to separate the delivery spring housing and the plunger, applying a delivery force to a bung. A latch mechanism latches the delivery spring housing at a forward position, preventing rearward movement of the delivery spring housing following release of the plunger.
