Primers
In my opinion it would be hard to statistically proove that one brand of primers will give better accuracy than the other one if loads are tuned to them. At least I have never felt much of a difference between Remington Federal or CCI. I was shooting Federals when by chance I stumbled upon 100.000 pc of Eropean Hirtenberger primers for a very reasonable price. I will probably not use them all up in my lifetime and I shoot just as good or badly with them as with any other brand. I am talking Benchrest rifle capable of sub .200 aggregates. Unfortunately I am not capable of that except once upon a blue moon.
BA