I was screwing around 3 or 4 years ago with this same thing.
I used the exact same powder load, bullet, and OAL.
I'd load 4 with one kind of primer, shoot them over a chrono, then reload the same 4 cases with a different primer and do it again. I used Rem, Fed, Win and CCI's. I did trim everytime too to make sure the cases stayed exactly the same.
Its wrote down somewhere, but if I remember right, I got 200fps difference and 2" difference in group size at 100yds between the 4 brands.