Abstract: An explosively operated tool (1) for driving a fastener into a substrate such as steel or concrete has a resetting mechanism (12) for resetting a piston (10) of the tool into a rear part of a barrel assembly (8) of the tool after each firing of the tool. The barrel assembly (8) is mounted for axial movement within the tool housing (2) and co-operates with a mass mounted for rearwards movement relative to the housing (2) in opposition to a biasing force to absorb recoil on firing of the tool. The resetting mechanism (12) for resetting the piston (10) into a rear part (2a) of the barrel assembly after firing is powered in response to displacement of the mass on recall.