"The benefit in a finely tuned target rifle with finely tuned ammunition is generally quite positive."
My experience does vary and not in "beat up old range rifles", whatever that is!
The proven benefits of loading close to the lands in single shot target rifles (BR) is variable but they frequently do gain some from that practice. BUT, the "carefully tuned" ammo for those tightly chambered rifles is NOT the same as we typically use in factory sporters.
Seating in the lands is not magic. BR bullets are typically lightly held in thin turned necks. Seating close or even hard into the lands with those rifles helps the load to attain proper ignition and peak pressures to assure a proper powder burn with the best powders for the cartridge. (It's really NOT to help the bullets to enter the rifleing straight as convenitonal wisdom suggests, but it MAY help that, a little. Fact is, concentric ammo will feed bullets into the lands quite consistantlly no matter the jump.) Thus, Walkalong's observation in his #9 post applies.
Normally large, to the point of being sloppy compared to BR rifles, our factory chambers allow standard - thick - factory case necks to hold onto bullets much tighter. Thus factory sporters DON'T benefit much, if any, and that rarely, from setting bullets against the lands because doing so can raise peak pressures more than is needed for the rest of the powder burn, potentially degrading accuracy.
Bottleneck cases run higher pressures because they're rifle cartridges, not because of the necks. Both rifles and handguns benefit from having a proper time-pressure curve but that's normally achieved by choosing the proper burn rate powder and primer for the load, not how they headspace.
YMMV.