I really think that someone had be at the top of their game before weighing primers is going to be a deal breaker. There are so many other variables at 600 and 1000 yrds I’m not sure there is any scientific way to test the effects of weighing primers but I would like to see someone run this test.
You will need a control group of 50 loaded rounds where every component is sorted except primers .
You will need an experimental group where each component is sorted including primers
That’s the easy part. The difficult part is to determine how to fire these rounds to test .
It is important that the shooter only knows that there are two groups of ammo not which one has sorted primers.
I would think that he would shoot one five shot group with both in a close time interval. Let things cool and reverse the order. That would give 10 groups of each and if there is a pattern of more consistscy it should show up. You could do this which reloading technique to determine whether it is actually worth the effort. One thing that I have kept records on ( actually apprx 2500 rds ) was the effect of bullet run out in the loaded round. I will tell you if definitely makes a measurable difference on paper.