The HiSCORE experiment is an array of wide-angle, non-imaging detectors of atmospheric Cherenkov component of EAS operating in the ultra high energy range. Whereas arrays of particle detectors use shower front of secondary particles that reach the observation level, HiSCORE deals with the shower light front, i.e. temporal and spatial distributions of Cherenkov photons generated in EAS. The temporal difference between light fronts of gamma and proton induced EAS is analyzed using Monte Carlo simulations. A gamma-hadron separation possibility based on this difference is studied taking into account realistic detector resolutions of event reconstruction.