In order to develop optimum coal grind (particle size distribution) for maximum bulk density, the packing of coal particles of different size distribution systems, such as the Gaudin-Schuhmann, Rosin-Rammler, lognormal and Johnson's SB distributions, has been studied theoretically and experimentally. It is shown that because of the limited size range available in reality, the packing of particles may be strongly affected by the method used to construct a given size distribution. The predictability of the linear-mixture packing model proposed earlier is confirmed by the good agreement between the measured and estimated packing densities. The usefulness of the theoretical approach to the optimum packing problem in practice is demonstrated. Some special techniques in such an approach are also discussed.