A further modification of the Hopkinson pressure bar has been developed for the accurate measurement of the force-deformation response from impact of single particles and particle beds. The striker employed is a steel rod that is driven by gravity. The procedure for calculating forces and deformations using this device is described in detail. A model that combines principles of Hertzian contact theory and the theory of longitudinal wave propagation in rods has been proposed and predictions are compared to forces and deformations measured experimentally under one- and two-point contact configurations. The excellent agreement between theory and experiments demonstrates the high accuracy and reproducibility of the device and the calculation procedures used. The greater instrumentation available along with the fewer assumptions required in the calculation of deformations than its predecessor-the Ultrafast Load Cell (UFLC)-makes it a particularly useful tool for in-depth single-particle breakage studies. Measurements on rock particles have shown that the device was able to detect deviations in the materials deformation and fracture response from what is expected assuming perfectly brittle behavior. (C) 2004 Elsevier B.V. All rights reserved.