McJ Tools Bronze chamber Brushes are designed to meet or exceed military specifications, thus to satisfy the shooter who wants the best tools to maintain his or her guns. All brushes are 8-32 threaded. Each brush contains the maximum number of bristles that can be inserted for the caliber. The phosphor bronze chamber brushes and chamber mop fit precisely into the chamber. Bristles are made from high quality bronze, which is aggressive enough to scour away lead fouling, copper fouling, and power residue.