An explosively actuated fastener driving tool of the type having a driving piston for driving a fastener at the forward end of a barrel upon firing of the tool has a retractor pawl assembly with a pawl for resetting the piston into a rear end of the barrel by forward movement of the barrel relative to the receiver following firing. The pawl assembly is so constructed that the pawl can be withdrawn from the barrel to permit removal of the barrel for routine cleaning and maintenance but in this condition the assembly still remains attached to the tool to prevent components from being misplaced.