[4] Hillberg developed a variety of insurgency weapons, primarily multiple barrel shotguns, which could be covertly distributed to partisan forces fighting in the United States' national interests.
In addition to aircraft projects (including the B-17) Hillberg completed a prototype .30 caliber carbine at Bell, which had been started at Pratt & Whitney.
[2][6] Hillberg left the aircraft industry in 1951, and went to work for High Standard Manufacturing Company in Hamden, Connecticut, as head of research and development.
In addition to High Standard pistols, Hillberg worked on new designs for the J. C. Higgins brand of guns for Sears, Roebuck & Company.
[2] In the late 1980s, Hillberg and Robert Schuets, owner of Olympic Arms Inc., worked together to bring the Whitney Wolverine back to the market.