FL dies are prone to runout, even when partially resizing. Hence the body die/neck sizer approach. Additionally, when using the neck sizing die only, no lube is required - makes life easier.
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With modern CNC machining dies are usually acceptable for what the average shooter requires and likely better.
However, this isn't the case when shooters are looking for that one hole group on a consistent and controllable basis.
When brass cases re fireformed for one chamber or even several chambers cut with the same reamer to exacting tolerances, brass doesn't flow as much when only the necks are sized and there is less wear and tear on the cases, even if they're loaded hot.
Bench Rest shooters found this out a long time ago.
Fire forming cases to fit into several or even a couple of different rifles, with slightly different chambers is a recipe for disaster on a hunting trip and that's one of the reasons there are so many proponents of full length resizing for all hunting applications.
I've seen rifles that will shoot anything they're fed with off the shelf new commercial ammunition, extremely well. If you have one, keep it because it's a JEWEL.
Not always but they mostly have tight chambers, that are reamed almost exactly aligned with the axis of the bore and their bolt faces, locking lugs are square to the axis of the bore.
Modern ammunition, is better than ever, especially the premium types.
There was a time, not that long ago when 4 inches with factory ammo our of an off the shelf rifle was considered to be acceptable at 100yds.
Today, many manufacturers, even of mass produced firerms, guarantee ONE inch or less accuracy WITH SPECIFIED AMMO. This was only available from ''custom'' builders at one time.
Most new manufacture rifles will deliver sub two inch groups at 100 yards with off most off the shelf ammo. Just fine for hunting out to 300yds, which is about the max 95% of shooters should shoot. If you're one of those nimrods that insists on taking head shots, FIFTY YARDS should be maximum