You can check concentricity, but the next step may be turning the necks.
Brass flows up when you resize the body, that's why you have to trim, and the necks get thicker.
With a thinner neck, the case tight in the chamber and the bullet set to kiss the lands, the bullet finds it's own center.
I don't like too thin necks, although that helps accuracy so I don't cut much, just to take off the high side.
I would just use the Lee collet die as long as it works.
Also, a few questions... why bump the shoulder after 4 rounds unless needed, and if you are annealing, as long as the primer pockets are tight why toss the brass after 12?
That's your choice in the matter, but if you're consistently shooting .5 groups now you're pretty much on the right track with what you are doing now.
Sub moa is good enough to win FT-R if you are good at calling wind.
