August 7, 2013 The Otis B.O.N.E. Tool was designed specifically to clean the bolt carrier assembly area of .223 cal./5.56MM rifles. Share this gun video:Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Tumblr (Opens in new window)