Cylindrical specimens of the AISI 1340 alloys were heat treated to produce martensitic, dual-phase or pearlitic structure and subjected to impact loading at strain rates ranging between 1000 and 8000 /s. The martensitic test specimens were tempered at 205, 315 and 425 ºC to determine the effects of tempered condition on the adiabatic shear failure of the alloy. The effects of geometry on strain localization and adiabatic shear banding in both alloys were investigated by subjecting cylindrical-, cubical-, and truncated conical-shaped specimens to high velocity impact. The dynamic torsion test involved rapidly twisting of heat-treated thin-walled tubular specimens of the alloys and determining the damage evolution during the high strain torsional loading. Both optical