When accurizing a factory rifle a re-crown is one of the things I normally do. I have seen a real deterioration in the QC done on factory weapons these last few years even to the point of a friend who bought a 22-250 Remington that had NO crown. They had simply lathed off the end of the barrel(it also lacked an ejector spring). So I would always look first but the crown is very important and if it's not right the rifle simply won't shoot. Also I've seen more of this type problem than bad barrels. I have seen a few bad chambers but most will shoot better thab the shooter can hold.