A misaligned crown can have a devastating effect on a rifle's accuracy. It’s a very common problem in factory rifles. Every second counts in mass production and factories don’t have the kind of time necessary to produce super accurate crowns.
This is not always the case as technology has improved over the years and many of the leading manufacturers are producing very good crowns on their guns, but there are always a few that escape and many shooters seek to have this improvement carried out on there rifles.
A lot goes into producing a 100% perfect crown and if factories were to put this kind of time into them, their production would slow down immensely making costs rise significantly and the end product less attractively priced.
I've seen huge improvements over the years by simply recrowning the factory rifle. I've had clients getting ready to rebarrel their rifles on numerous occasions when all that was needed was a recrown.
The barrel is placed in a four jaw chuck in the lathe and dialled into within .0001 of 1mm and using a single point cutting tool a tiny amount of material is removed leaving a perfect crown.