So I have looked at a lot of barrels (factory and custom) with my bore scope and this is much more common than people probably think. It is also one of the first things I look at for a barrel that will not shoot. My experience is that barrels that look like this (usually worse) often do not shoot as well with the bullets close to the lands but can shoot very well with significant jump.
I will say that I see this very common on factory and not unusual on pre-fits but is very rare when the chambering is done at a quality shop. Most of the those places do some pretty amazing work and manage their quality very well. It all comes down to technique and attention to detail when indicating everything into place.
I will say that I see this very common on factory and not unusual on pre-fits but is very rare when the chambering is done at a quality shop. Most of the those places do some pretty amazing work and manage their quality very well. It all comes down to technique and attention to detail when indicating everything into place.