Plastic flow instabilities and, in particular, their manifestations as submit-crometer size shear bands remain a highly debatable phenomenon in experimental studies, while they appear very naturally in numerical simulations of plastic defor-mation of highly inhomogeneous materials. Performed numerical studies reveal a considerable impact of the initial dislocation density on the amplitude of velocity dispersion behind a shock wave front. The simulations show an almost linear increase of the dispersion with the impactor velocity, and the dispersion effects appeared to be much more pronounced for copper and aluminium alloys rather than iron. The presence of inclusions, such as second-phase precipitates, can increase the value of the dispersion amplitude several times and make it mechanically meaningful. At the same time, the further increase of inclusions’ fraction above several volume percent leads to the decrease of both – the elastic precursor amplitude and velocity dispersion. Analytically, the effect of micro-localisation can be considered using the integral criterion of plasticity based on the fading memory concept with the range of characteristic relaxation times.