Re: S1, more seating depth questions
I think excessive neck tension is counterproductive to accuracy. I should have been more specific. What I really meant to say is, "Use a full length sizing die that incorporates a changeable neck bushing in its design, thereby removing the need for an expander ball and giving better control over neck tension, and more concentric ammo."
If one of the goals is to load concentric ammunition, neck wall thickness must be very consistent, requiring turning necks with most lots of brass. Long range shooting also demands controlling vertical stringing, which in turn demands controlling neck tension. Turning necks will help these issues:
1) Standard Deviation of Velocity
2) Concentricity of ammo
3) Accuracy (vertical stringing)