What about sorting by weight ?
I've seen some shooters take and
weigh their rounds .
Many shooters have sorted by various methods because they, like so many, want to see if it gives better performance.
On RFC there's a poster by the name MKnarr who's done a lot of testing by different sorting methods. He said he "found absolutely no correlation between weight or rim thickness and velocity spread and I have statistical correlation plots to prove it." See, for example, his posts in this thread h t t p s ://www.rimfirecentral.com/forums/showthread.php?t=1192085&page=2 He has many other similar posts and observations elsewhere on RFC (and perhaps elsewhere).
There's another sorting method previously not referred to in this thread -- sorting by concentricity. Bullet concentricity may have some variance, particularly in inexpensive ammos. But for match ammo, no one does it except as an experiment and it, like other sorting methods, is not used by serious, high level competitors. For a recent and brief discussion on sorting by concentricity and its lack of success, see h ttp://www.rimfireaccuracy.com/Forums/showthread.php/13324-ammo
No one who is shooting competitively at high levels sorts ammo by rim thickness, weight, base to ogive length or concentricity. These shooters rely on lot testing. There is no other reliable method to finding the best ammo and achieving the best accuracy.
When using less expensive varieties of entry level "target" ammo, there may be a psychological benefit to using various sorting methods. In other words, by taking every step available to try to get these ammos to shoot like something else, a shooter can tell himself he tried everything. It won't significantly change how it shoots but the shooter will know he did almost everything possible.
I said "almost everything possible" because the only way to improve results is to find better shooting lots of match ammo. Less expensive varieties can be very capricious or odd and peculiar in their performance. That is to say, the will have more group size variation -- some small and some twice as large or more. They tend to have more velocity variation, with larger extreme spreads. And significantly, they will have more individual rounds having POI that are not expected by their MV and are due to factors that can't be easily identified. (I'll try to post more about this in this or another thread.)
There are not shortcuts to finding the best performing ammo.