Primers
Different brands of primers may or may not make a difference in the accuracy, velocity, or pressure of your load. I once was working up a load fot a 30-30 336 Marlin, using 150 bullets and WW748. Using CCI 200 and 250 primers the groups run 2"-2.50". After changing to a Federal 210 primer the gun would shoot under an inch. I could cite a few more situations was switching primer made a big difference. Most of the time changing the primer will have little effect, but sometimes it will. I've taken good loads to exceptional loads by changing primers. The best place to start is the primer listed in the source of the load. When I get a load that shoots good, I will then try different brands of primers to see if I can improve it. I think I have a box of every primer made on my loading bench. Be careful when changing primers. Lower the powder charge and work up to your original powder charge, while watch for pressure signs. 8)