An injection device for holding and actuating a pre-filled syringe including a barrel holder having an axial passageway adapted to hold the barrel of the pre-filled syringe, a grip movable relative to the barrel holder to move a plunger of the pre-filled syringe, the grip configured to be locked to the barrel holder to prevent axial movement therebetween and unlocked from the barrel holder to permit axial movement therebetween, and a needle guard arranged to retract into the barrel holder in response to force against an injection site to unlock the grip from the barrel holder.
