Various optical devices are utilized to fire artillery in Korean Army. To transport and store the optical devices, some cases are made up for a set. The covers of cases are made of Glass Fiber Reinforced Plastic(GFRP) and resin. Because of materials of case, it has a disadvantage in productivity for manufacturing covers and assembling components. In this study, ABS resin is presented for alternative and verify possibility through FEM analysis. Comparing with GFRP, max stress-ratio of ABS is decreased 19.6% for bottom, 8.2% for side and 25.4% for edge. Also each strain is changed 17.3%, 180.3% and 17.7%. According to the research results, ABS resin is considered possible for alternative. And the number of components is decreased for around 73.8%.