Abstract: The barrel temperature of the 95-1 automatic rifle is too high and firing dispersion is high after multiple shots are fired. Using 5.8 mm bullet as the research object, an in-bore motion model under the coupling of multiple physical fields is established and verified by firing tests. Based on the basic principle of heat transfer, the influence of different bullet jacket materials on the motion in hot barrel is studied by the finite element method. The results show that, under room temperature, the in-bore swing angle of copper jacket bullets is smaller than that of copper clad steel ones. With the increase of barrel temperature, the in-bore swing angle of copper jacket bullet increases significantly. Under the same pressure, the muzzle velocity of copper jacket bullets is lower than that of copper clad steel ones. After firing 30 and 60 rounds, copper bullet muzzle velocity decreases by 2.2 m/s and 1.8 m/s, respectively. The in-bore motion time is increased by 2.6 μs and 4.7 μs with the increase of barrel temperature. After firing 30 and 60 rounds, the muzzle velocity of copper clad steel bullets decreases by 0.7 m/s and increases by 1.4 m/s, and the in-bore motion time decreases by 1.7 μs and 0.8 μs, respectively. The research results can provide theoretical reference for the design of small-caliber ammunition.

Key words: jacketmaterial, firingaccuracy, in-boremovement, hotbarrel, multi-physics