Abstract: The shooting experiments were conducted to investigate the bore damage characteristics of a machine gun barrel and analyze the failure mechanisms. Optical microscrope, scanning electron microscrope (SEM), endoscrope, and guage are used for observation and measurement of barrel bore. Results show that the main failure mode of Cr layer along the gun barrel transits from spalling to wear. According to this characteristic, the spalling, transitional, and wear zones are identified along the axial direction of gun barrel. From spalling zone to wear zone, the initial damage location of rifling moves from the groove to the land. The damage rates in both spalling and wear zones are relatively higher, and the damage rate in the transitional zone is relatively lower. In the spalling zone, at 27% lifetime, the Cr layer peels off with large pieces; at 55% lifetime, the Cr layer peels totally off. In the wear zone, for only 7% lifetime, obvious wear occurs in the turn guide side of the land; when the lifetime is increased from 7% to 14%, the bore inner diameter is enlarged from 12.69 to 12.75 mm. Key

Key words: barrel, damage, failure, erosion, wear