Yes it is possible that the clean barrel is causing a difference in your POI. But with the Black Horn 209 powder that seems strange. Although I only tried the powder in two rifles which is hardly a test. All rifles are different.

Some thoughts on Black Horn powder. I shot two pounds of the Black Horn powder and was VERY IMPRESSED with the powder, the accuracy,theway it shot, and the way it cleaned up. Although it did push the grease back, off the breech plug pretty bad. I think it took me longer to clean that area then it ever did. Also cleaning with solvent VS cleaning with soap and water.. solvent is expensive, you have to keep a supply in the house, and on a personal note, strong solvents react to the skin on my hands in a uncomfortable way... Soap and water is all over the house, and easy to remember where it is.

While I got some excellent accuracy with BlackHorn 209 and it seems to have excellent power, I had to ask myself; Is BlackHorn worth the price over say Triple Se7en or Pyrodex, is the fact I can not find it locally a reason to stick with the old stand by powders, am I generating more needed down range power or what I have with the old standby powderplenty, and which has a bigger chance of misfires... Very few have tested this powder in snow and rain conditions...

Were you getting better more consistant groups with a different powder? You might want to try the rifle from that stand point. Or since you are shooting Black Horn Powder.. fowl the barrel with about 40 grains of it. Then hunt with it that way.