Primers do make a difference in accuracy. I have a custom Rem 700 with a Shilen 26" SS #6 barrel 25-06. It was finicky to get it to shoot as well as I thought it should. That is until I started fooling around with different primers. 49 grs IMR 4350, Rem case, BINGO CCI 250 mag primers, 117 Sierra Pro Hunter, 3000 fps and BUG HOLES.