RE: Clean barrel or Dirty
When at the range I clean every 5 to 10 rounds. Once I finish brushing and patching I run two tight fitting patches with Gun Scrubber through the barrel to remove the oil and residue left by the solvent. If you can' t find Gun Scrubber rubbing alcohol or brake cleaner (yeah you heard right) works just as well. I have found that if I completely remove all the oil etc from my barrel my POI is the same as a dirty bore.
As a ritual on my last visit to the range prior to deer season (usually the Friday afternoon before ) after checking my zero for the hundreth time I clean my rifle as normal, and de-oil the bore as I described. I then fire two " fouler shots" followed with a run through with a dry bore snake. It' s pure superstition but it works for me.