The effects on the thermal response of pressed polymer bonded explosives caused by varying their components have been assessed at two extreme heating rates using the Super Small-scale Cookoff Bomb. Tests were primarily conducted on RDX-based compositions containing 5% ethylene-vinyl acetate binder with varying amounts of PETN or TATE. Some experiments were numerically simulated using a one-dimensional finite difference code. The simulations are not able to predict the violence of the thermal response, but do accurately reproduce radial heat flow in the test assembly and satisfactorily predict both the time to thermal response and the surface temperature at response for the mixed explosive compositions. The influence of the ratio of the mixed explosives on the type of thermal response observed is discussed and several compositions which give very mild thermal responses have been identified.