Composite materials are engineering materials that have become widespread in the aerospace, defense and automotive sectors due to the improvement of their mechanical, thermal and tribological properties in recent years. One of the most important types of composite materials preferred in the defense industry is polymer composite material. Polymer composite materials are used in the manufacture of light guns due to their high strength, heat and humidity resistance and thermal properties. In order to make these properties more effective, natural fibers are used as reinforcement elements. At this point, it is necessary to proceed to the decision stage in the selection of reinforcement element for polymer composite material in light gun bodies. In this study, the Critic method was used to determine the criterion weights for the selection of materials, and the Topsis, Saw and Marcos methods were used to determine the order of importance for the selection of the most suitable natural reinforcement material. With these applied methods, three different ranking results were calculated and converted into a net ranking with the Board Count method. The correlation between the methods was revealed by using the Spearman correlation coefficient. It has been determined that the most suitable reinforcement for the PA 66 plastic material used in light gun bodies is the banana fiber material. The Young's modulus, which has a criterion weight of 0.180, was determined as the most effective criterion.