This is way back in my memory and something that users have no control of, but I believe it was Federal that did a big research program and found besides rim thickness, that the way the primer material was spun into the rim had a big effect on accuracy. Back in the 1994 time frame they cam out with their match grade ammo and the US Olympic team used it along with other countries. At $12/box, I never tried it. Don't beat me up too bad,as I said it is from my memory which I use mostly to forget with
