Abstract: A method of reducing the erosion of surfaces of gun components on which there is flame impingement is provided. A thin coating containing metallic aluminium is applied to the surfaces, and is subsequently exposed to the hot compressed gases formed on firing. This causes diffusion of the aluminium into the surface, which reduces erosion. The coating may be applied either by the direct application of a paint containing metallic aluminium to the gun component then firing the gun, by applying such a paint to projectiles which are then fired from the gun, or by fitting a hollow frangible ring containing a composition which includes metallic aluminium around the body of the projectile, and then firing the projectile. The coating may advantageously contain aluminium silicide. A number of paints and compositions suitable for the invention are described.