US Army still working on ERCA ‘rotating band' fix

The US Army is continuing to refine its Extended Range Cannon Artillery (ERCA) prototypes in anticipation of delivering 18 platforms to soldiers in 2023 for testing. However, the service's decision to switch the munitions' ‘rotating band' material from copper to nickel has not solved the gun tube erosion conundrum, according to Brigadier General John Rafferty, head of the Long-Range Precision Fires Cross-Functional Team.

Also called a ‘driving band', this component is a soft piece of metal near the bottom of a munition and is often made from a gilding metal, copper, or lead. Each time a round is fired, the pressure of the propellant forces the metal into the rifling of the barrel and a seal is formed to prevent gases from blowing past the projectile. This engages the barrel's rifling to spin and stabilise the projectile.

“The copper rotating band that all the artillerymen know on the outside of our 155 mm projectiles is perfect for a 20 ft gun tube because it protects the projectile and the gun tube on the way out; it provides the seal, makes sure that there's no engraving on the outside of the projectile … and also protects the wear on the gun,” Brig Gen Rafferty told an audience on 31 August during an annual Fires Conference.

However, under the army's ERCA initiative, it is incrementally upgrading BAE Systems' Paladin M109A7 self-propelled howitzer to include the addition of a 58-calibre, 30 ft (9.1 m) gun tube so that the platform can launch 155 mm rounds out to 70 km. To reach such a distance, the weapon uses a ‘supercharged' propellant to fire current and future munitions such as the M982 Excalibur, XM1113 Rocket-Assisted Projectile, and XM1155 Extended Range Artillery Projectile (ERAP).