The shock initiation threshold of hexanitrostilbene (HNS) pellets with different densities has been investigated by performing small-scale gap tests. As the sensitivity of HNS strongly depends on the density of the pellet, the density was varied in a range that the pellet material can be expected to be insensitive by means of no initiation at pressure loads of 2.6 GPa. In the case of HNS we observed that the material became insensitive at densities larger than 1.65 g cm(-3). Further, we found that the pressure loads can be increased from 2.6 GPa to 3.29 GPa for densities increasing from o = 1.65 g cm(-3) to Q = 1.70 g cm(-3) (98% TMD) without detonation of the HNS pellet.