DEVELOPMENT OF A STELLITE-LINED, CHROMIUM-PLATED BARREL FOR 5.56MM MACHINE GUN

The procedure as developed by Springfield Armory for design and fabrication of a stellite-lined, chromium-plated barrel for the 5.56mm machine gun is described. Results of erosion tests of the stellite-lined barrels, standard barrels, and two other types of barrels show that the stellite-lined barrels are superior in erosion resistance. One of the stellite-lined barrels was fired 43,994 rounds prior to rejection. A maximum of 12,476 rounds was fired from one of the standard barrels prior to rejection. The two other types of barrels - a standard barrel with a nitrided bore and a barrel of two-piece construction - were fired 29,874 and 990 rounds, respectively, before rejection. The two-piece barrel has an 18-inch forward section made from Cr-Mo-V steel and the rear section, including the chamber, is made entirely from stellite. All barrels were rejected on the basis of the projectile instability criterion - 15 degrees yaw of 20 per cent of the projectiles fired. All barrels were fired at an average rate of 200 shots per minute.