Wear of Projectile Rotating Bands

Rotating or driving bands are bands relatively soft materials surrounding a projectile. They have a number of functions the chief of which is probably that they produce stabilizing rotating of the projectile when they are engraved or keyed into the rifling. These bands are used on spin-stabilized projectiles as small as 20 mm caliber, but this discussion concerns especially the larger cannon, i.e., in excess of 105 mm. Excess wear of projectile rotating bands has a number of important negative consequences including inaccuracy and short rounds. There are two distinctly different mechanisms of wear. At low speeds near the beginning of motion, wear is by adhesion, abrasion, and even under some conditions, scuffing. After a few centimeters of sliding, a thin surface film of molten band material is formed and the remainder of the sliding is melt-lubricated. While metal-on-metal sliding is limited to the first few centimeters, it is very important and can result in serious wear problems down bore. The exact wear of rotating bands depends on the motion of the projectile in the bore of the cannon. Therefore, this motion can be inferred from the wear.