Birchwood Casey MSR Chamber Brushes helps remove copper, carbon and lead fouling from rifle chambers. Thread size 8-32. Bronze bristles scrub the chamber, neck and shoulder of a MSR. The steel bristles at the base scrub the star chamber of the locking lugs on a MSR. Product Features • 5.56 & .223 caliber • Thread size 8-32 • Helps remove copper, carbon and lead fouling from rifle chambers