Since darn near as many bore brushes get used in the shop as get sold, weâ€™ve packed these custom-made, top quality brushes in bulk paks to make them more convenient and less expensive. The shank is one-piece, looped and wound (not two, twisted together and chopped off). Nylon Bore Brush - New generation bore cleaners attack copper and bronze-based bullet jacket fouling aggressively and are just as hard on bronze cleaning brushes. Our nylon brushes stand up to these super cleaners and wonâ€™t cause accuracy-ruining scratches. One-piece, looped and wound steel shanks (except Black Powder (BP) series, .17 cal., and .20 cal., which have brass shanks). Mfg: Brownells SPECS: Bristles: Available in nylon. Shank: Steel, looped and wound. Rifle: 3Â¼ (8.3cm) OAL, .17 and.20 cal. 5-40 threads, all others 8-32 thread. Pistol/Revolver: 2-1/8 (5.4cm) OAL, .17 cal. 5-40 thread, all others 8-32 thread. Shotgun: 2-7/8 (7.3cm) OAL, 5/16''''-27 thread.