Cast bullet shooters hear and talk a lot about leading. Leading in, and in front of throat. Leading near muzzle. Leading mid bore. Leading easily removed. Leading "soldered" to bore. Leading that appears as tiny flecks on first patch but doesn't seem to do any harm. Ways to remove leading, etc.
However, I can't remember reading about lead build up in the neck of the chamber. With my memory that doesn't mean that it isn't in some writings about cast bullets but it certainly isn't usually in the instructions about shooting cast bullets. Yet, it happens in my rifles and I suspect I am not the only one.
Maybe we don't hear about it because it doesn't hurt anything and most of us don't peer into our chambers with a bore scope so don't know that it happens.
The leading in my chambers sometimes looks to be getting quite thick and it isn't always uniformly distributed around the neck so could cause the case to be pushed out of alinement. For those who still worried about neck tension variations in spite of the evidence it might be a cause. Who knows - it could be the cause of those times when a load and rifle won't shoot well for unknown reasons.
At any rate it probably doesn't improve accuracy although even that could be a possibility. It would be nice to either prevent or easily remove it and eliminate one more possibility of screwy thing happening. It can be removed by rotating an appropriate size bronze brush in the neck but it takes some elbow grease and I could do without it.
To figure out how to deal with it it would be good to understand what causes it. But I suspect as with other things related to knowing exactly what happens the instant things go pop, we will have three kinds of shooters. Ones that don't know, ones that think they know but don't know, and those that know they don't know.
Anyway I would like to hear about your experience in preventing or removing leading in the chamber neck. Is there any evidence that it hurts or helps accuracy?