The purpose of this report is to present the SHMS Heavy Gas Cherenkov (HGC) detector Geant4 simulation results pertaining to e/pi separation between 1.3 GeV/c<p<7.2 GeV/c using C4F10 and CO2. This report assumes that the pi/e production ratio at the simulated momenta of p={1.5GeV/c, 3.0GeV/c, 5.0GeV/c, 7.0GeV/c} is pi/e={230, 20, 0.36, 0.0039} respectively. Based on our study, we recommend using CO2 at P=0.50atm.