As Cayugad said this may vary somewhat from gun to gun, I have also found that it will vary according to the cleaning and oil you use.
I try different things and got different results, what I am using now with BH209 is Hoppes #9 and alcohol and when I am going to hunt I use Sheath or Barrier [same thing just a name change by the co. that makes it] with this my first shot is on the upper edge of my regular group. Lee