In shock-wave physics, emphasis has changed from obtaining Hugoniot states to examining the properties of those states. States prepared by initial shocks can be probed by second waves. The overtaking wave experiments use this idea to obtain sound speeds in shocked states. Such a study(1) was done on PBX 9501. The diagnostic technique in the overtake experiments uses the radiation from a shock front in a covering material. In addition, explosive/window release measurements have been done with the VISAR technique. When one applies these techniques to a less ideal explosive such as PBX 9502, one finds initial transient effects and structures in release curves. ©2000 American Institute of Physics.