First shot in the group

I have tested this theory out about 5 times so far with good results. But not set in stone yet. My gun is over 100 shots without cleaning and getting better ever range session. The night before I shoot, i pull the breach plug and clean primer residue out with a drill bit. Next I run 3-5 tite bullets completely thru bore to clean oxidation off of rifle lands. Just some 250 sst i have laying around.  reinstall bp and bolt. The first shot is in the group. This is on paper with by 300 yard group from a week ago. I would like some one else to verify this really works.