Like others I have tried different "break in" procedures and honestly never found much difference. The first thing I do is clean the firearm completely before firing, this includes a very light lap of the boreof a factory barrel with JB. On the range no need for stacked groups, 3 shots max but I prefer the first range session to shoot 1 or maybe 2 then let it come to ambient before shooting again. Since your first range session is about sighting in and getting use to the new tool, there is little need to concern yourself at this point about groups or finding the right load IMO. AMy intial range session is often 10-12 shots. I then fully clean the bore, including copper cleaning and another light pass of JB's if I think it needs it. My second range session pretty much mirrors range session one, keep the heat down by going slow. Another full cleaning and now I start looking at potential s for accuracy and loads. I have cleaned my rifles after every range session for years and no problems of excess copper fouling, I found I don't need to brush it as often as leaving it for a few.A bore guide &1 piece coated or carbon fibre rod are essentials IMO.