Summary form only given. This paper reports on the design and fabrication efforts of a supersonic, high-mass electromagnetic launcher. The program goal was to efficiently accelerate an existing M933/934 mortar round to over 400 m/s. The basic electromagnetic architecture chosen was a railgun, with a detailed system study undertaken to determine the optimal railgun configuration. Operational limits required that the overall launch package have a mass of less than 18 kg and a length of less than one meter. The peak acceleration was required to be less than 10 kG, and no launch package components could be discarded in flight. In addition, the program required a laboratory demonstration, which when coupled with the schedule and budget constraints, required that the existing IAT electromagnetic launch facility (ELF) be capable of providing the prime power.