the purpose of breaking in a bbl is primarily for this, to remove from inside the bbl, any machine/ tooling marks, plus any other junk left over, since it was proly not cleaned before you got it. Most use this as a typical break in: after each shot, clean and lube and dry for 5 shots. then do 5 shot strings or groups, clean after the 5th shot, do this for 5 sets. After the last set , clean and lube real good, dry patch it, then shoot till your hearts content. the first cleaning and lubings before this last one? Just one pass with a brass brush, and push out with dry patch, then lube with one patch, then dry out with one patch.