[Unclenick]

When the .308 Win was invented everyone said it would never shoot well because its neck was too much shorter than the one on the .30-06. When the .223 Rem was invented, everyone said it would never shoot well because its neck was too much shorter than a .222 Rem neck.

The dire predictions were not born out. As long as your neck length is great enough to keep an adequate grip on the bullet, you should be able to devise chambers and loads that will work well together. That does not mean, however, that you can't design bad combinations. Leaving a bullet with so little grip on it that the neck can't keep it straight through feeding and chambering will be at a distinct disadvantage. I've seen up to 2 moa of group error documented from that in some chambers.

An observation made in a number of guns is that a second seating depth sweet spot is often found when bullets are somewhere around one caliber into the case mouth. If you could have a one caliber seating depth achieved at the same time your bullet nose was at its happiest distance off the lands, you would likely be pleased with the effect.

More neck grip means more starting force for the bullet, or at least higher pressure build before it gets moving, and that tends to help with muzzle velocity consistency and barrel time consistency. These are most often issues for long range trajectories, though, note that long range is relative to the extreme range of the bullet. A handgun is affected by velocity variation at a shorter range than a rifle is.

So those are potential factors. Like everything else they will matter much more in some guns with some load components than others.