In the most common approach to detect trace explosives at security checkpoints, any illicit residues must first be removed from the surface of interest (contact sampling) before they are delivered to a detector, such as an ion mobility spectrometer. Contact sampling involves applying a compressive shearing load to dislodge the residue from a surface. Optimizing this step requires an understanding of the properties of the residues and their effect on residue behavior. This study seeks to evaluate the previously unstudied effect of the binder mechanical properties and particle size distributions on the behavior of Composition C-4. Composition C-4 demonstrates complex granular behavior, and contains a highly viscous, non-Newtonian binder. In addition to studies of real C-4, simulated C-4 was created with mechanical properties very similar to the real composite. The results with the live and simulated C-4 indicate that - while highly important - the binder is not the only driving parameter controlling granule deformation under load; to create an effective simulant the binder must be combined with particles of an appropriate bimodal particle size distribution.