Production of nanocrystalline RDX at elevated expansion pressures was investigated. Increasing the expansion pressure from 1 bar up to 60 bar results in an increased particle size. At high expansion pressure, the particle size is strongly dependent on the pre-expansion pressure within the saturator. Increasing the pre-expansion pressure from 280 to 350 bar, the mean particle size is reduced by over a factor of 2. Operation of the RESS process with high expansion pressure is significantly less energy consuming. However to attain particle size below 200 nm it may be essential to expand to lower pressures. The response of recrystallized RDX to initiation stimuli such as impact and shock was compared to the response of conventional RDX. The preliminary finding indicate that samples consisting of pure nanocrystalline RDX as well as compositions with 88% RDX and 12 % binder show a significant reduction in sensitivity with respect to conventional RDX.