<p>High-entropy alloys (HEAs) are compositionally complex materials distinguished for their high performance under extreme loading conditions. This study uses molecular dynamics to investigate how Mo addition affects the high strain rate tensile behavior of monocrystalline body-centered cubic AlCoCrFeMo_x HEA. Results reveal that at high strain rates, shear-band-mediated plasticity dominates over conventional dislocation-mediated mechanisms, where lattice distortion cannot provide strengthening through reduced dislocation mobility. Additionally, no chemical short-range ordering between atomic species was observed as an alternative strengthening mechanism. A weighted average-based design parameter, <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\updelta }_{shear}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">δ</mi> <mrow> <mi mathvariant="italic">shear</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>, was introduced to quantify shear modulus mismatch among elements. Increasing <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\updelta }_{shear}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">δ</mi> <mrow> <mi mathvariant="italic">shear</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> correlates with material softening due to enhanced localized strain, leading to reduced yield strength. Finally, an optimal concentration of constituent elements in the HEA was determined by minimizing <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({\updelta }_{shear}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">δ</mi> <mrow> <mi mathvariant="italic">shear</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>. The study offers insights for the design of AlCoCrFeMo_x HEA systems and proposes a new design criterion for maximizing yield strength under high strain rate loading.</p> Graphical abstract <p></p>