Speer used to make 275gr. .333 bullets but I don't know if they do anymore.
Maybe cheap bullets for the 8X56R could be used in the 318 like these:
http://www.grafs.com/retail/catalog/category/categoryId/925?

I don't have a 318 right now, but would agree that it would be much easier (read cheaper) to get ammo together for it. On the 30'06 brass of course.

I would like to see some hardness testing of the reduced diameter bullets as well as some cross sectioned bullets to see if the jackets are loosening.
Suppose in the BGRC shoots it doesn't matter much as far as construction integrity, but on game it may be a different matter.