A large-caliber railgun was developed to demonstrate the supersonic launch of 120-mm projectiles. A trade study that evaluated over 70 different railgun configurations and geometries resulted in the selection of a high-inductance-gradient multiturn configuration as the best overall choice. Subscale tests were performed on both the railgun and launch package configurations. A full-scale laboratory system was installed, which included a dedicated high-current large-caliber breech and gunline. A full-scale launcher was successfully tested to beyond the design conditions. This paper will describe the trade study and overall experimental program that included the subscale testing and full-scale design and experimental results.