Just to add ... it seems generally recognized that perfect truth (in the perpendicular ....... or ''normal'' to bore axis) ...... is critical, the last 1" of the barrel affecting accuracy more than any other single feature.
If you consider a damaged crown ... then just at the instant the bullet leaves barrel .. there can be a gas-pressure ''push'' slightly off axis .... as gas escapes preferentially in one direction to the side ....... this at 100 yds and plus, will be potentially well over MOA category.