Studies on the regression rates of three compositions of paraffin wax‐HTPB hybrid fuel grains in a stream of gaseous oxygen using two different swirl injectors at a fixed injection pressure were carried out. It was found that the regression rate in the hybrid fuel increases with increasing paraffin wax percentage, which may be attributed to melt‐flow effects. The local regression rates, average regression rates, fuel mass consumption rates, and total mass fluxes for the hybrid fuels were found to be dependent on the swirl injector configuration. All three hybrid fuels were characterized by scanning electron microscopy (SEM). Furthermore, the thermal stability and thermal degradation behavior of the hybrid fuels were investigated by DTA/TGA techniques.