Re: .416/.338 Cartridge?
Sdiehn, it's easy to get confused with that book.
The figure he lists is a solid case measure, not internal capacity.
In other words, if you took, say, a 30-06 case and filled it with lead, he'll tell you how much water would be displaced by the entire case. It's something his CAD software will do automatically, so he included it.
He mentions it in the copy at the front of the book, and that it has a very limited usefulness in comparing one case to another.