Rifle/Pistol 3¼" (8.3cm) long, 8 32 thread except for .17 cal.. The natural spring of wool helps the mop conform easily to rifling grooves; the looped and twisted brass shank wool bore mops 35/38 wool bore mop, dz and coupling won t scratch the bore. A classic favorite for wool bore mops 12 ga wool bore mop, dz gun cleaning; virgin wool mop holds lots of bore cleaner or oil, so both ends of the barrel get thoroughly coated. Shotgun 2 7⁄8" (7.3cm) long, 5⁄16" 27 thread.. Wool, brass shank and coupling.