Abstract: This invention relates to composite gun barrels along the lines that a bal be made of two or more different materials and of different outer diameters for optimum life and performance at different points along the length of the barrel. A composite gun barrel according to this invention includes a breech joined to a muzzle through a mid-section of the barrel by inertia or friction welding. Such a breech, muzzle and mid-section or mid-sections are made of different external diameters and wall thicknesses and of varying materials. A material more resistant to high temperature erosion and of larger outside diameter for high gas pressure is utilized at the chamber, while the material and wall thickness selected for use near the muzzle is optimum for frictional wear and lower pressure. A hot work tool steel such as H11 containing 1.5% Mn, 5% Cr, 0.4 V and 0.35 C is employed at the origin of rifling.