No downside I can think of--heck a wetherby rifle has so much freebore that the bullet is out of the case before it's in the rifling with some bullets!! However just for giggles (if it's bothering you) try seating them about .050" back from the rifling. Thats a number that barnes likes to use to try and keep pressure under control and many people say they get great accuracy there. AND just using some of my bullet comparators I would have to say that much factory ammo is made to make about that kind of jump in many hunting rifles. Could be worth a try --theres very likely a "sweetspot" further back than by the rifling.

Neck tension becomes more important to keep the bullet from shifting when you have less bullet in contact with the neck....like the earlier comment, try it at the range and see. Load a full magazine, shoot all but the last, check it for signs of bullet shifting, repeat until you are confident that it will or will not work. The worst that will happen is that the bullet will shift back into the case from recoil...but if it goes very far at all I would suggest you look at the neck tension of your loads. In a .308Win I would EXPECT (never tried it) no problem from .2" of neck holding the bullet. It just isn't a hard enough kicker...

FWIW, I have tried all the way down to 110 Gr Sierra JHP in a 300WSM. Long story, but in the end I had less than .1" of the bullet seated and still was short of the lands. Of course, there is only about .25" if bearing surface on that bullet anyway! They functioned fine as long as I single loaded them. I wasn't brave enough to fill the magazine and see if they stayed put.

The neck lengths on the 7.65 Mauser and th .300 Savage have necks about .230 long. That's not very much but it seems to work. roger