primers
I've found Federal Primers--Gold Medal--work for me--I had a chance to try 1000 primers iof different brands and types n the same 4 loads and had the least variation in chronograph info and groups size with them. That being said, the difference was not very big at all. If you are looking for a primer alone to shave off a 1/2 MOA from your group--it's not going to happen.