A combustion chamber system, for use within a combustion-powered fastener-driving tool, comprises a dual combustion chamber system comprising a pre-combustion chamber and a final combustion chamber. The pre-combustion chamber is characterized by a high aspect ratio and has different obstacles fixedly incorporated therein for selectively retarding and enhancing the rate of burn and the rate of speed of the flame front propagating through the pre-combustion chamber. In addition, an obstacle, having a predetermined solid geometrical configuration is disposed within the final combustion chamber at a position immediately disposed downstream of a port fluidically interconnecting the pre-combustion chamber to the final combustion chamber so as to cause the flame front to diverge and split into multiple components which flow radially outwardly throughout the final combustion chamber.