i use a 45-70 rifle brush -the way to do it is get out your reloading manual,look at the dimensional drawing of your case- ie the distance between the walls- and then go up a few thou- ie for a 30 cal, you use something on the order of a 45 , a 223 takes about a 9mm,- most bottleneck cases have a straight sided "version"-then you can either use the plunge method like they do in the ar's or a rachet type like they do in the m14s- for some of the heavy magnums, you may have to go to a shotgun brush