It's been many years since I did any reloading, but I got to admit this is one question that never came to mind in making up my reloads.
I'd be curious to know what capacity/volume each case holds - neck sized vs. full length.
Of course, would have to weigh the cases first to have two as near to identical as possible.
In theory, I think you may be right. Would be interesting to load up about twenty cases.
Load 10 neck sized only, and 10 full length sized. Test 'em by firing over a chrony, and
see what results you get - what the avg. for each bunch comes to.
If you do, please post and let us know how it comes out.