A tool for inserting a marker into tissue at a biopsy site includes an elongate plunger having a blind bore. A plunger rod has a proximal end received within and secured to the blind bore so that the plunger rod moves conjointly with the plunger and a spring is secured to the distal end of the plunger rod. A cannula has a lumen that receives a distal end of the plunger rod and a crimp is formed in the cannula near its distal end. The cannula has a side exit port where a marker is ejected from the lumen. A ramp is formed in communication with the side exit port and the ramp has a preselected slope that controls the angle at which the marker is ejected. The marker is ejected from the side exit port into tissue when the spring unloads abruptly as the marker clears the crimp.