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This document describes a method for measuring forces during an impact between a soft or frangible projectile and a relatively rigid flat normal surface. The document describes the hardware and instrumentation required, as well as the processing and data reduction required to compute force. In this test, a projectile impacts one end of a long cylindrical bar with flat ends, called a Hopkinson bar. The impact occurs on the centerline of the bar in the axial direction. The diameter of the cylindrical bar is large compared to the lateral dimension of the projectile so that, during and after the impact, the projectile material moves radially or backward, rather than extruding around the perimeter of the impact surface. The bar is instrumented with strain gages at some distance from the impacted end to measure the longitudinal strain in the bar.