<p>This paper presents the results of an experimental assessment of the effect of loading rate on the deformation of structural steel of ordinary quality and high-strength steel Miilux Protection 500 in impact compression tests. Dynamic tests were carried out on a modernized test stand based on a pneumatic coper PK-80 in the load range of 45–117 m/s. In the cross-section of the model material samples, a significant transformation of the microstructural components and a change in the shape and size of the grains after loading, mainly in the central part, was observed. An increase in the average microhardness value by 20% was recorded for the tested samples, and the heterogeneity of the deformation processes in their cross-section was noted. The studies have shown that the kinetics of local deformation of samples made of high-strength steel Miilux Protection 500, which is used as an armor material, is realized by different mechanisms. At a loading rate of 48–88 m/s, the effect of shock wave attenuation on the density of defect distribution in the martensitic structure of the material was observed. The formation of localized deformation was recorded under compression at a load rate of 117 m/s. The width of the formed adiabatic shear band was 4–5 μm and was located perpendicular to the main crack and the plane of separation of the sample. In the areas near the crack, the microhardness of the steel increased to a maximum value of 750 HV compared to the average value of 580 HV. The obtained results of the impact compression experiment made it possible to establish the relationship between the loading rate and the transformation of the microstructure of steels of different strengths, as well as to assess their tendency to form zones of local deformation.</p>