diff in ES between virgin brass and once fired brass

[MontanaRifleman]

It's probably true that we don't have enough info.
My thinking is if the ONLY change was fired -vs- unfired, it leaves little other than capacity & load density.

Also, about you load density, try this:
At the range, load a shell with the barrel pointed up, carefully lower to rest, and fire across a chrono. Note that your MV went up.
Now do the opposite, with barrel pointing down on loading.
Note that the MV goes down.
Do the same test with fast chambering -vs- slow, and watch your ES.

I think you'll find that it's a good idea to develop with the fastest powder(for capacity) -that fills a case well.
And whatever load you've hit on in low case fill can be matched in higher case fill, using QuickLoad.

I agree that higher case density is a good thing. I may try your experiment sometime.