Shotgun 2 7⁄8" (7.3cm) long, 5⁄16" 27 thread... A classic favorite for gun cleaning; virgin wool mop holds lots of bore cleaner or oil, so both ends of the barrel get wool bore mops 17 cal rifle wool bore mop, pkg thoroughly coated. Advise cal long, 8 32 thread except for .17 cal. Rifle/Pistol 3¼" (8.3cm) wool bore mops 4dz/more r/p wool bore mop. The natural spring of wool helps the mop conform easily to rifling grooves; the looped and twisted brass shank and coupling won t scratch the bore. Wool, brass shank and coupling.