Particle-in-cell (PIC) simulations confirm recent multi-component plasma-opening switch measurements in which magnetic field simultaneously penetrates the heaviest plasma components while pushing the lighter species. In these simulations a positive potential hill associated with the J×B force develops that, in the frame of the moving hill, reflects the lighter ions but is not large enough to reflect heavier ions. The simulations show that species separation can occur when the Hall speed is large compared to the characteristic speed for the heavier species but small compared to the characteristic speed of the lighter species.