Effect of Rifling Grooves on the Performance of Small-Caliber Ammunition

摘要

A combined experimental and computational investigation was performed to examine the effect of rifling grooves on the aerodynamics of projectiles and determine whether the aerodynamics associated with the rifling grooves are a potential mechanism for in-flight trim angles. The experimental program consisted of spark-range firings of bullets from the standard twist barrel spanning the range of velocities typically encountered in flight. Additionally, sabot-launched smooth and pre-engraved bullets were fired from oversized barrels with twist rates to match in-flight spin rates and velocities. The computational technique was first validated using existing wind tunnel data for a rifled projectile. Computational results were then obtained to complement the results from the spark-range testing. The results show that the aerodynamic components most sensitive to the rifling grooves are the Magnus force and moment and the roll-damping moment. These effects are relatively small for typical in-flight conditions and are unlikely to produce trim angle effects and can be ignored in future computational and experimental efforts.