Abstract: An injector includes a housing that has a proximal end and a distal end that extends along a longitudinal axis. A medicament container contains a volume of a medicament. A button coupled to the housing is rotatable about the longitudinal axis between a locked position and an unlocked position and movable along the longitudinal axis between a pre-firing position and a firing position. A latch is at least partially disposed within the button, a ram is movable relative to the latch, and an energy source urges the ram distally along the longitudinal axis. The ram is prevented from moving relative to the latch by the button in the pre-firing position. Rotation of the button to the unlocked position and movement of the button distally along the longitudinal axis relative to the housing into the firing position allows the ram to move relative to the latch.