Needle assisted injection device having reduced trigger force

An injector, comprising:

• a container containing progesterone or an analogue of progesterone;
• a trigger mechanism including:
• a trigger member disposed about an axis, the trigger member having a trigger member opening wall and a trigger member protrusion, and
• a ram assembly having a ram configured to pressurize the container for expelling the progesterone or analogue of progesterone from the container, the ram assembly further having a trigger engagement member configured to engage the trigger member opening wall when the trigger member is in a pre-firing condition;
• an energy source associated with the ram and configured to power the ram to expel the progesterone or analogue of progesterone;
• and
• a user-operable guard including a guard aperture receiving with the trigger member protrusion, the user-operable guard configured to cause an axial translation of the trigger member in a proximal direction from the pre-firing condition to a firing condition in which the trigger engagement member is disengaged from the trigger member opening wall to allow the energy source to fire the ram,
• wherein the energy source expels the analogue of progesterone at a stream velocity of at least about 100 centimeters per second.