Development of 20mm and 30mm Plastic/Aluminum Cartridge Cases

Basic feasibility was established for the 20mm and 30mm plastic/aluminum cartridge cases under this program. The case design consists of a plastic body joined mechanically to an aluminum base forming a composite assembly. Work on the 30mm case was limited to Mann barrel firings while the 20mm case was fired successfully in both a Mann barrel and the M61 automatic gun at a rate of 4300 rounds per minute. Test firings of the 20mm case in the M39 gun, however, were unsuccessful. The effort on the 20mm case progressed into a development program including high and low temperature firings in the M61. Satisfactory case performance has been established at the temperature extremes (160 F and -65 F) and at ambient temperatures with the case design being developed as far as possible within the scope of this contract. Various plastics materials filled with glass fibers were tested. Nylon 612/43 percent glass gave the best results.