Particles with spherical shape and specific size distribution are major considerations in achieving high performance, solid loading and mix fluidity in processing of energetic materials for high explosive/rocket propellant applications. Spherical 3-Nitro-1, 2, 4-triazol-5-one (NTO) of specific particle size distribution (PSD) was prepared by a proprietary process and the powders were characterized by X-ray powder diffraction, thermal and spectral methods. Present study explores the spherical-NTO of specific particle size D (4.3) of 150, 100, 25, 15, 10, and less than 5 mu m and their bi/trimodal mixtures for their micromeritic properties. From the packability and flowability constants, bimodal mixture of coarse (150 mu m) to fine (25 mu m) ratio of 70:30 is found to be optimum for processing in explosive formulations. Paste explosive formulations were made based on identified bimodal mixture and their flow behavior studied by viscosity studies. The study inferred that spherical particles of NTO bring down the viscosity by about 75% for the same explosive content to binder ratio in comparison with non-spherical-NTO. Porosity data also supports the same for improvement in explosive loading by 10% by the usage of spherical-NTO over non-spherical particles for the given explosive to binder ratio. (C) 2013 Elsevier B.V. All rights reserved.