Hornady Brass Weight Variation

[BD1]

I think that within one lot of brass from the same manufacturer, that has been fully and consistently prepped, case weight is about as close as you are going to reasonably get. Measuring case volume in gn of H20 is something I do fairly often as it is a significant variable needed for Quickload. The issue is the meniscus. It takes some practice to find the "overflow" and then match that meniscus without going too far. And the variation from concave to max convex meniscus can easily be a grain. I typically take five or six cases of the same weight and then use the average of those case volumes in grains of water to get the value for Quickload. I can't even imagine trying to sort a couple hundred cases by water volume.
Different lots of brass, even from the same manufacturer, can vary significantly. I have sorted thousands of .223 brass over the years, and it all varies somewhat lot to lot.