Explosive powder charge operating setting tool

Explosive powder charge operated setting tool having a setting direction for driving fastening elements into a receiving material and comprising means forming an axially extending piston guide (4) having a leading end and a trailing end spaced apart in the setting direction, said means forming an axially extending guide bore (11) for an axially extending driving piston (1) displaceable therein in the setting direction from a trailing initial position to a leading driven position, said means forming a cartridge chamber (6) at a trailing end, an axially extending bore (7) in said means connecting said cartridge chamber (6) and said guide bore (11), said means having a base surface (5) at a trailing end of said guide bore (11) forming a contact surface for a trailing end surface of said driving piston, said base surface (5) extending perpendicularly of said axially extending guide bore (11), an axially extending housing part (8) laterally enclosing and spaced radially outwardly from said piston guide and forming an axially extending channel (9) in flow communication with said cartridge chamber (7), said piston guide (4) having an aperture (10) in a leading end region thereof connecting said channel (9) with said guide bore (11), a closeable passageway (12) in said housing part (8), valve means (13) connected to said channel (9) and displaceable between an open position and a closed position for forming a storage space in the closed position, and a spacer element (2) for spacing the trailing end surface of said driving piston (1) from said base surface (5), said spacer element (2) having a stop face (3) extending perpendicularly to the axial direction of said piston guide (4) and having a smaller area than said base surface (5), and said stop face (3) spaced laterally outwardly from and asymmetrically relative to said driving piston axis.