FN AR15 barrels are hammer forged using the same proprietary highgrade Chrome MolyVenadium steel used in FNs venerable machinegun barrels produced to handle the punishment of sustained fullyautomatic fire. After forging, each barrel is Magnetic Particle tested to ensure that it is free of microstresses or flaws, resulting in consistency and quality in every barrel shipped from the factory. The bore and chamber are chrome lined to help resist corrosion and provide resistance to heat erosion which greatly improves barrel life and reliable chambering/extraction. The M4 style feed ramps and barrel extension provide consistent feeding and the matte black Manganese Phosphate finish resists external corrosion and oxidation.