Bullets, .323" can easily be sized to .318", I believe some, if not all, of the .318" bullets offered by Buffalo Arms (and maybe Reed) have been resized from .323" to keep the customers from having to do it. In my experience the 8x57IR/IRS shoot better with bullets closer to 200 grains, than very light ones. I believe this is because the throats that were reamed long enough for the original 200 + grain (237? gr) bullets, leave the light (short) bullets unsupported after leaving the case neck and before engaging the rifling. This is just one person's experience, however.
Mike