Whata ya mean be the same?
Internal capacities of different brands vary within the same caliber. I've only studied .223, and just as a novelty really, and even the same makers brass will vary by year class or run, like Lake city mil brass.
Not tryin to be rude, but what are ya after in the end run with your question? Maybe we can help if more specific.
Guys use water because it fills the entire case with no air space between something like stick powder. Then the info is usually used to sort cases by similar capacity to remove another variable.
Water by volume weighs close to many powders, esp true 2f(ffg) Black Powder), but not all powders of course.
Noslers book and listed load info shows case capacity of different powders by % of the case filled with different loads.