Improved needle free injectors comprising of a energy sources, triggering mechanisms, impact members, and drug delivery pistons are disclosed. In one preferred embodiment, the triggering mechanism comprises a spool which seals an energy source comprised of compressed gas and a component for releasing the spool to release the pressurized gas and urge a ram forward to force a drug containing formulation through a drug delivery orifice. The device may include a cap covering the orifice and safety mechanisms to prevent accidental delivery
