Evaluation of Obturator and Sealing Cuff Properties for the M865 Training Projectile with Comparison to Ballistic Testing

Abstract : The nylon obturation and RTV sealing cuff for the M865 training round were evaluated to identity potential sources of ballistic variability associated with the material properties and material processing. While the properties of these materials are strongly dependent on processing conditions, temperature, and moisture content, the M865 performance variability is reduced by a well-engineered fracture mechanism that focuses the stresses in the obturation during sabot discard. A ballistic test was developed to validate the study. For the ballistic test, obturators were manufactured in "brittle," "tough," and "tough-wet" conditions. These three conditions produced significant differences in the mechanical properties (the maximum strength varied by a factor of 2, the elastic modulus varied by a factor of 25, and the elongation to failure varied by a factor of 10). However, the ballistic performance did not show any significant variability due to the obturation properties.