Military weapons designers earned average annual salaries of $75,000 as of 2014, according to the job site Indeed. The minimum educational requirement for this job is typically a bachelor's degree in mechanical engineering, which takes between four and five years -- with an internship -- to complete.op Pay In State of New York. Average salaries for military weapons designers varied the most in the West in 2014, according to Indeed. They earned the lowest salaries, $60,000 in Hawaii and the highest salaries, $100,000, in California.