A pin puller comprising a piston having a pull shaft extending from a cylinder in which the piston is slidable, is actuated by an explosive charge which, when ignited, develops a pressurized gas that is directed, through a transfer tube, into a chamber extending through the piston and into the piston shaft, from which it is directed outwardly through a port in the shaft into a sealed space behind the piston, to move the piston in a direction to exert a pull upon the shaft and a pull-actuated device connected thereto. The piston slidably receives the transfer tube and is sealed thereto to prevent short-circuit escape of the pressurized gas to the leading side of the piston. An electric circuit is provided for igniting the explosive charge when energized.