Highly reactive nanocomposite powders with compositions xAl+MoO3 were synthesized using arrested reactive milling (ARM). Three compositions with x=4, 8, and 16 were prepared using powders of Al and MoO3 as starting materials. The objective of this work was to identify the optimized composition of fuel-rich nanocomposites for use in energetic formulations. X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), particle size analysis, and heated filament ignition tests were performed to analyze the nanocomposite powders. Results indicate that nanosized domains of MoO3 are uniformly distributed in Al matrix for all three powders. The crystallite size of Al in all three samples is in the range of 35-45 nm. The size of nanocomposite particles increases with the increase in aluminum concentration. The ignition temperatures of the nanocomposite powders also increase at higher aluminum concentrations. Results of DSC performed at different heating rates indicate several overlapping exothermic peaks occurring in the temperature range of 400 - 900 K. Additional exothermic and endothermic peaks are observed at higher temperatures. A correlation between the kinetics of low-temperature DSC peaks and ignition kinetics measured at substantially higher heating rates is observed. A similar observation was made earlier for the ignition behavior of stoichiometric Al-MoO3 nanocomposite powders.