Birchwood Casey 6.8mm/.270 Cal Rifle Bronze Cleaning Brush Birchwood Casey single pack bronze cleaning brushes are tough on removing copper, carbon and lead from firearm barrels. Thread size 8-32 and are available in multiple caliber sizes. Specifications and Features: Birchwood Casey Bronze Cleaning Brush 6.8mm/.270 Caliber Rifle 8-32 thread pitch Bronze Bristles