Westinghouse quickly decided to copy the G7e, and "went to work with a speed and fervor that was dazzling" (certainly in comparison to NTS's languid pace). Design was complete by mid-April, and a contract for 2,000 Mark 18s, 2,020 warheads, 543 exercise heads (for training shots), tools, spares, and workshop gear was issued 2 May. The first test models were delivered just 15 weeks after Westinghouse started work and the Mark 18 was promised to the Submarine Force by summer 1942.