A low retraction activation force plunger sub-assembly (200) for an automatic injector (100) includes: a plunger outer (220) having one or more engagement prongs (220A), a plunger inner (210) having a shoulder (210A), and a plunger biasing member (270) retained in a first energized state between said plunger outer (220) and plunger inner (210) when the engagement prongs (220A) of the plunger outer (220) are releasably engaged with the shoulder (210A) of the plunger inner (210). An automatic injector (100) includes a housing (14, 16), an activation mechanism (12), an actuation mechanism (10), and a syringe cartridge (20) having the plunger sub-assembly (200) and a needle assembly (40), wherein the actuation mechanism (10) comprises an actuation biasing member (102) residing in an initial energized state substantially within an upper portion of an actuation pill (104). A method of assembling the automatic injector (100) includes the steps of: assembling the plunger sub-assembly (200) and inserting the plunger sub-assembly (200) into the housing (14,16) such that a proximal end of the plunger sub-assembly (200) contacts the actuation pill (104).
