Measuring case capacity

[aardvaark]

So I did some reading recently about measuring internal case capacity and it sure makes a lot more sense than sorting by weight which is what I have always done.

But when I started doing this, a few questions came to mind that I would appreciate answers for:

So far I’ve measured case capacity after firing before any prep. Partly because you need the spent primer in there to hold the water. Or should I resize first? Or at what point in the case prep should I be measuring internal capacity?

I’ve only done some once-fired brass. And it was fired in the rifle that I’ll be using this brass in. What a huge variable! And this is measuring brass that I had already weight-sorted.

What spread do you folks allow for the different size cases? 270Win 22-250 204R 17Hornet