Stark Industries ∑-Series Specialized Ammunition. The "Sigma" series specialized ammunition was originally designed for use with weapons made by the company of INGENE. INGENE however, was shut down, and was later transformed into the Trust, and from the Trust, as we all know, sprang Stark Industries The Sigma series comes in a variety of forms, and to date, can only be used with certain types of weapons. These weapons will be listed before.