Lapua brass is another story with that combination. The expander ball is a much harder pull and runout is not nearly as good as with the WW brass. And it's not as accurate as WW. No way WW brass is "better" though.
Of course, it could be the difference in case volume too.
It's both. Been there and checked that.
BTW, how do you lube the inside of the case necks?
