Neck bushing dies
The only dies I've ever used have just been your "plain Jane" 2-die sets from Redding, RCBS, Hornady, and Forster. But if you had a rifle capable of 1/2 MOA precision, would there be an advantage to using one of the neck-bushing dies. I don't know a lot about them, but as I undertand it, you insert a different sized bushing, depending on how far below bullet diameter you want to constrict the neck. This affects how much tension is holding the bullet in place. I guess if all your bullets are held to the same tension, they'll all leave the brass at the same pressure.
Wouldn't my plain Jane die apply consistent tension as well, although it wouldn't be adjustable. What's the advantage of being able to play with the degree of neck tension? Wouldn't a pricey seater die that assured good bullet concentricity with minimal runout do more for accuracy?