This is a subject close to my interest. I am a retired mechanical engineer my main expertise was maintenance and machinery failure.
There are some hard facts in accuracy and the maintenance of the barre.
Fact 1 Barrel manufactures states that a very clean barrel is the most accurate. Rifle barrels have 2 charactristics (excuse spelling) bore must be dead striaght and centered. rifleing must not vary in depth. A barrel fouled will cause uneven rifleing and cause bullet unbalance.

Fact 2 Many shooters report that their barrel shoots more accurate dirty and fouled.

I personally am a super clean barrel freak and find that my barrels shoot more accurate clean.

I have a feeling that the dirty barrel accuracy is very true but caused by several factors. Including method of barrel breakin, cleaning style, . Bullet type and brand used. I would like for you shooters could report some facts on how you breakin and shoot. And how many shoots fired makes your gun shoot the most accurate. How did you maintain your barrel when new.
Thanks