Some carbon deposits are so baked on that nylon and bronze can't touch them - that's when you need stainless steel bristles. This is the most aggressive gun cleaning brush in the lineup, designed for the worst fouling on internal metal parts: bolt faces, gas system components, heavily caked locking lugs, and any surface where carbon has hardened under extreme heat and pressure over hundreds of rounds.

Stainless steel bristles will scratch blued finishes, cerakote, and anodized coatings - so this brush stays away from external surfaces entirely. It's strictly for the internal metal parts that nobody sees but everyone needs clean. The AR-15 gas key is a prime example: carbon builds up inside the key and around the mounting screws where heat is highest, and softer bristle materials just slide over it. Stainless steel breaks through that crust. The same goes for the bolt face after corrosive-primed ammunition or after thousands of rounds without a deep clean.

Use this cleaning brush as the last resort, not the first pick. Start every gun cleaning session with nylon for general surfaces, step up to bronze for standard carbon, and bring out the stainless steel only for the deposits that resist everything else. The double-ended design puts the aggressive bristles exactly where you need them - large end for flat surfaces, small end for recessed channels and tight grooves.