Why is over-cleaning a problem?

A freshly cleaned bare-metal barrel often shoots worse than the same barrel with a thin lead film.

After a deep clean, expect 30 to 200 shots before accuracy returns as the bore leads in again. Aggressive bronze brushing wears the bore. Steel rods bouncing against the crown can damage the muzzle, which directly hurts accuracy. The rule is: do not clean unless accuracy has actually fallen off, and when you do, clean gently from the breech with a patch and light solvent.