My experience that the easiest/quickest way to tune a load for accuracy is by varying the seating depth. I've not seen that changing powders or primers has that much effect on accuracy. Changing bullets will greatly affect accuracy but I usually have a preferred bullet I want to hunt with already chosen and I'll stick with it unless I just can't get it to shoot. I usually pick several powders from the loading manual that give top listed velocity and work up the charge over my chronograph. Loading manual velocities are not known for being very accurate and usually one powder will prove to give better velocity with reasonable pressure. Once I've settled on a powder I'll start varying the bullet seating depth. Most of my rifles shoot best with the bullet almost touching the lands.