Abstract <p>In this study, the influence of key mechanical processing parameters in a planetary ball mill, including jar rotation speed, milling duration, and speed ratio between the jar and the planetary disk (parameter <i>K</i>), was investigated with respect to the formation of composite reactive particles for self-propagating high-temperature synthesis (SHS) involving powders of varying ductility (Ni–Al, Ti–Si, Si–C). Both low-energy and high-energy ball milling were found to induce significant changes in particle morphology, amorphization of the crystal structure, and mechanochemical transformations in the studied systems. The results highlighted the critical importance of processing parameter control for tailoring the properties of composite materials. The synthesis of layered, multicomponent composites based on Ta/Ti/Nb/Zr/Hf, intended as precursors for subsequent SHS of high-entropy compounds, was demonstrated. Additionally, methods for producing reactive spherical Ti/Al powders and for surface modification of spherical AlSi10Mg powders for additive manufacturing applications were developed. Adjustment of parameter <i>K</i> influences not only the structure and particle size of the milled powders, but also the initiation temperature of SHS reactions. Optimal values of <i>K</i> facilitate the achievement of minimal ignition thresholds, whereas deviations from these values lead to a decrease in the reactivity of the powder mixtures. These findings confirm that the careful selection of milling regime and <i>K</i> value allows effective control over grinding, mechanochemical activation, and mechanochemical synthesis, opening new opportunities for the fabrication of nanocomposite materials with tailored functional and structural characteristics. This capability is of significant relevance to the development of advanced materials across a range of applications, including additive manufacturing and synthesis of high‑entropy compounds.</p>