Abstract: According to the present invention there is provided an explosively-actuated tool for use in setting fasteners into a substrate, comprising a barrel (2), a driving piston (6) mount within the barrel for driving the fastener into a substrate upon detonation of an explosive charge positioned at or adjacent the rear of the barrel, a firing chamber (8) defined in the barrel rearwardly of the piston, and a system capable of controlling the power of the tool by controlled venting of combustion gases from the firing chamber. The power control system comprises an exhaust port arrangement (14) leading from the firing chamber through the wall of the barrel, and a control member (16) for controlling the effective open area of the exhaust port arrangement. Particularly advantageously, the end of the control rod is provided with a concave arcuate control edge (16b) which provides a relatively uniform relationship between displacement of the control rod and the degree of opening of the exhaust port arrangement.

Abstract: The barrel of a power actuated tool for driving a fastener into a substrate upon detonation of an explosive charge, comprises front (4) and rear (2) barrel sections mounted for telescopic movement to absorb recoil upon firing. The sections are held in assembled relation by a retainer element (14) and are such that assembly and disassembly can occur by manipulation of one barrel section relative to other without the need to remove the retainer element (14).