Power control arrangement for an explosive powder-driven setting gun

Explosive powder-driven setting gun comprising a casing forming an axially extending first bore having a muzzle end and a rear end spaced axially from the muzzle end, a piston guide axially displaceably mounted in the bore in said casing, said piston guide having a muzzle end and a rear end spaced axially from the muzzle end with the muzzle end of said piston guide oriented relative to one another in the same manner as the muzzle end and rear end of the bore in said casing, said piston guide forming a second bore with the axis thereof disposed in substantially parallel relation with the axis of the first bore, an axially elongated driving piston axially displaceable through the second bore in said piston guide between the rear end and muzzle end thereof, said driving piston having a forward end closer to the muzzle end of said piston guide and a rearward end closer to the rear end of said piston guide, a locking piece located within said casing at the rear end of the bore rearwardly of said piston guide, an axially displaceable stop pin mounted in the rear end of said piston guide and having the axis thereof disposed in parallel relation with the axis of said driving piston, said stop pin having a front end facing toward the muzzle end of said piston guide and a rear end facing in the opposite direction, wherein the improvement comprises that said locking piece being axially stationarily mounted in said casing, said stop pin being axially displaceable relative to said piston guide for locating the front end of said stop pin within the second bore in said piston guide to limit the position of the rear end of said driving piston relative to the rear end of said piston guide, and a supporting element for the rear end of said stop pin, said supporting element adjustably mounted in said locking piece and arranged for varying the extent to which said stop pin extends into the second bore in said said piston guide.