The most important part is to start with really good brass.
Say LAPUA.
Without regard to the dies you use the best dies can not fix bad brass.
The game here is CONCENTRIC, just as in building a great preforming engine.
Setting up your dies properly is also very important.
Get your self a concentricty gage and see what your results are.
With good brass maybe all you need is a set of Lee Collet Dies
