Otis 50 Cal Bronze Bore Brush

This is the 50 caliber bronze bore brush from Otis. Big bores collect fouling in a hurry and there is a lot of surface area to cover, so a full diameter brush with bronze bristles is the tool that does the actual work in a cleaning session.

Bronze is chosen for bore brushes because it is softer than barrel steel. It scrubs carbon and copper without attacking the rifling, and it wears out before the barrel does, which is exactly the trade you want. Treat the brush as a wear item, wet it with solvent, and follow with patches until they come out clean.