True Story.
I was shooting in Texas with Gene Beggs, in his
tunnel. We were shooting full-boogie short-range benchrest rifle with his 6mm Beggs cartridge (similar to 6 PPC). The more we shot the smaller the groups. But after 40-45 rounds or so I could tell Gene was getting antsy. He really, really wanted to clean that barrel, though our groups were getting smaller.
Anyway, I relented and told Gene he could clean the barrel after we took a lunch break. After we returned to the tunnel, I asked Gene to clean the barrel
exactly as he would at a benchrest match. He used a bit of abrasive cream, and then two different solvents. Lots of brush strokes -- at least 15. Back and forth.
When he was done we went back in the tunnel.... And the results were, to me at least, shocking.
The initial 5-shot groups were 1/2" or worse. Mind you this is a benchrest cartridge shooting in a TUNNEL. After 15 rounds we saw definite improvement -- all shots touching with the fourth 5-shot group, i.e. rounds 16-20. At about 25-30 rounds it seemed the peak accuracy was back. And we got some of the smallest groups of the day at about 35 rounds after cleaning...
YMMV folks. This is the story of one rifle, one barrel. Your barrel could be completely different.
I am not advocating not cleaning -- I am only suggesting that shooters observe empirically what shot-count/fouling condition shoots best with their gun and their load.