We picked a lights out load in our Match grade WOA heavy barrel 20" AR15, and we shot some groups of everything the same, except primer.
I have no explanation why the CCI primers did not perform like the Federal and Remington as we have many loads using CCI under MOA. CCA41 had 1 flyer, the other 2, had 2 flyers each, while the Federal (on right, normal federal SP) had 2 small flyers but they were barely off main group.
Also, for a CONTROL, we put in 2 groups using MIXED BRASS, to show how important using brass with very similar internal capacities are. Each one of these brass was internally measured for consistency and specifically chosen. Then we just took 5 brass of different brands, mixed and loaded it up using very precise powder and very precise bullets that weighed all within .02 grains or so.
We can see....uniform brass is BIG.