Abstract: In a combustion-powered, fastener-driving tool with a combustion chamber, a piston chamber communicating with the combustion chamber, a driving piston movable within the piston chamber between an initial position and a terminal position, and a driving blade mounted to the driving piston so as to be conjointly movable with the driving piston, the driving piston, the driving blade, and the piston chamber are arranged so that combustion in the combustion chamber imparts energy to the driving piston and the driving blade so as to drive the driving piston and the driving blade from the initial position toward the terminal position with the driving blade preceding the driving piston, over a stroke having a length sufficient to enable the driving blade to transfer more than eight tenths of the maximum, transferable energy to a fastener engaged by the driving blade as the driving piston and the driving blade approach the terminal position. The piston chamber has an inner, cylindrical wall.