I guess it depends on what you are expecting, as far as accuracy goes..
From my experience, Dad, brother and I always reduced our loads, in military cases a couple grains on 308 and 3006, providing we were at the top, of the chart.
If I am at the top, and I seldom am... I make absolute sure that I work up, to the top, and that the components are exactly the same as the the manual states in the load data.
As you said, all cartridges, including 223, or others that have a military heritage, the inside case capacity, will vary significantly, military to civilian.
What I did not first realize is, that even cases such as Federal American Eagle will be different than true Federal civilian brass. That said, like you... my loads are largely plinking, and not loaded real hot, so most of the time I do not sort real carefully.
I will say, that I have noticed accuracy variations, between different head stamps, with the same load. So, in guns that accuracy is important, I sort as best I can, cases by head stamp, in a effort to reduce shot to shot variations.
This, only for loads and rifles that are accurate enough to tell the difference. I have noticed shot to shot point of impact changes, and even pressure changes, as indicated by primer appearance in different head stamped cases.
The run of the mill AR-15 or Ruger Mini 14 are not probably not accurate enough to see any changes. At least in my experience.
I need to do the same thing, that you are doing, as I hope to go prairie dog hunting again, and need all the cases I can get. I will probably sort my with a lighted magnifier, and weigh a few random cases from the sorted piles to get and idea what cases are some what the same. Sorting and loading into lots, in a effort to improve my odds of producing ammo that will be consistent. I have a 1/2 of a 5 gallon bucket of it to go through, with mixed up head stamps..
Not sure what the best process would be?
Good luck with your work..