So, I'm trying to warp (sic) my tiny mind around the idea of measuring case volume. my concern is going from one brand of brass to another, or old brass to new brass, all within the same cartridge, and determining case volume before powder loading and velocity testing.

Does anyone have some thumb-nail suggestions for consistent accurate case-volume measuring?

I know that working up a load with new weight-sorted brass all of the same headstamp is by far the best-practice for consistent case volume control. But I'm getting more and more into obsolete cartridges, and NOS brass for those is getting more and more difficult to find, and of course the cost of powder to play with keeps going up... you know the story,

Thanks, for sharing Your considered experiences,
Jeff

Not exact, but I weighed the fired case, filled to the top with water. Used a collet bullet puller to hold a bullet at ~1 bullet caliber protrusion, raise the filled case slowly till the neck bottomed out against the puller. Wipe the case down and weigh again. The difference between the 2 should be close.

Use an umprimed, fired case.
Crimp the mouth a minimum just so it can hold a bullet and seat to desired OAL..
Weigh.
Fill it up with water through the primer hole using a syringe.
Weigh and subtract from unfilled weight.

That is the method I follow.

PS: a heavier case does not always imply less capacity.

I never really load a case to its full max potential capacity.

Learned that over time... makes life simpler so I don't have to worry about your problem above.

I don't need a 500 yd load capable of taking an elk or elephant at that distance, to drop a blacktail at 100 yds.

I shoot things at what I consider 30/30 ranges most of the time anyway, just like about what distance most game is taken.

Not pushing the max limits, I've found that I get a lot more case life, a lot longer barrel life, and a lot more shots out of a pound of powder, while still getting the job done.

but to each their own... good luck with your quest.

Not really about using 100% of max capacity John, I did it out of curiosity on whether weight sorted and capacity sorted actually affects overall performance and accuracy.
Found that those 2 things affect performance and accuracy very little in the grand scheme of things. Also if you go by Nosler data you can compare your capacity to their test brass.
Just because somebody says weight sorted match grade brass and charges more doesn’t mean the brass is worth a sh*t.

Haven't checked the weight difference, but I've read that the water should sit at least overnight before filling the case so all the small air bubbles can dissipate.

Step fill eliminates air bubbles and air pockets. Eye dropper and fill in 3-4 steps pushes any air from previous step out. Been used in the packaging industry for 40 years.

Thank You Gentlemen, for the very helpful hints! Now on to the water volume trials!