Where we are going requires us to take a certain route.
If I am trying to squeeze the last tiny fraction of an inch in accuracy out of high performance rifle, I will;
1. Weight cases of the same make and lot for uniformity and select those that have the same or near same weight which also will establish a lot of cases with equal internal powder capacity for uniform combustion.
2. Trim the cases to uniform length
3. Turn the necks for a uniform thickness and roundness.
4. Deburr the flash holes and uniform the primer pockets to assist in uniform ignition.
5. Fire form the cases to my chamber
6. Neck size only using a Wilson bushing die that does not require the case to be expanded for the bullet I am using.
7. Weight the individual powder charges
8. Seat the bullets in a Wilson straight line hand die
9. Anneal the cases every five firings.
If I am shooting a Krag, any other military rifle and most sporting commercial rifles, most of the above is a waste of time and at most will deliver .25 MOA better accuracy. If an extra 1/4 inch off the 100 yards groups is what you are after, the yes do all of the above.
The average guy, who is shooting the average rifle for hunting or recreational can skip 3 through 8 above and be as happy as a baby playing under a blanket. If he pays attention to the details of cast bullet shooting and fit, his rifle will shoot as well or better than it will be the best over the counter ammo.
Felix was a former benchrest shooter who applied his scientific mind to squeeze the last tiny smidgen of accuracy out of a rifle and load. I know how to do it as well, but I really don't care enough to spend the time and detail fussing around with minutia that won't make any difference in my life and gun fun. I suspect most folks on this board are of the same ilk. But it is good to know the very fine point if that level of accuracy scratches where we itch.
If was going to a bench rest match, I will load my ammo for that goal. If I am going out for fun shooting with my pals, I won't. The tiny details only matter if the last tiny bit of accuracy also matters.