Re: Case neck turning?
A practical approach to neck walls, regardless of what dies, or what brass, or what chamber you have, is to begin by understanding what is going on here.
The illustration below, albeit exagerated, shows a thick/thin neck, which is present to some degree in ANY brass you buy. Some are worse than others, but the brass manufacturing process is far from perfect enough to generate a perfectly concentric neck wall to the thousandth of an inch. This is why neck turners were invented in the first place.
"A" being the thin side, "B" being the thick side, and "C" being the "neck" of the sizing die, or bushing, or whatever, with the brass forced into it. Your die will force the brass back into as concentric of a circle as the reamer was that created it. What this means is that the brass is to spec on the outside of the case, with any variations being forced inward to the interior.
In the case of neck walls, the outside of the neck will be "perfectly" round and concentric, but the inside will be off of center with everthing else, to the amount of the difference of the thick side from the thin side, as shown in the pic.
Let's say that "A" is .013" thick, and "B" is .017" thick. That's a difference of .004". Regardless of the chamber you are using this starts the bullet out with an unacceptable amount of TIR.....not really good for "accuracy", if accuracy is the goal.
The only way to resolve this is to turn the .017" thick side of the neck down to close to the .013" thick side. In the practical application of this, if it's done right, the thicker portions of the neck are skim cut by the neck turning tool, the halfway in between portions are feathered out, and the thin side isn't even touched. This creates a better relationship to concentricity with the bore when the case is run into the die the next time.
Those who say turning necks for a "standard" chamber is not necessary simply do not understand the mechanics that TIR plays in the equation of accuracy, and the magic of starting a bullet out straight. If you are careful not to reduce the thin side of the case neck, and only skim off the thick side, then what is hurt regarding neck integrity, and how much is gained regarding reduced runout? What exactly is the difference between a thick/thin neck blown out to a standard chamber, and an even neck, other than, with the even neck, the interior of the neck now being concentric? How exactly does neck tension become affected to any derogatory degree with the neck now being an even .013" thick all through instead of thick/thin?
Turning the thick side of my necks off is a key part of my system, which produces very low runout, and all I shoot are standard chambers......