I was racking my brain trying to find an old article on engineering handloads for you and finally found it as an archived upload at usrifleteams.com. Do a google for "working up a match load DOE final draft" and it should be the first return. It is listed as a .ibf file but you should be able to open it with adobe reader.
If I remember right you've settled on a powder charge, settled on a seating depth, and now you are on to primers. My guess is that if you don't see any difference between primers you need to play with seating depth as well, and the article linked shows you how to do that, work with two variables at one time.
If you do see a difference with primers just go with the most accurate.
Machine guns are awesome until you have to carry one.