Uuuhhhh, having a 7-08 that shots .75" groups ain't no big deal. 'course if I had a load that did that, I certainly wouldn't change it.
I've tried blind mini test with mag primers and non mag primers and didn't see where they did anything for me. Not especially with ball powder however.
I loaded 10 rounds using mag primers and put them in a paper sack with a data post it. I loaded 10 rounds with standard primers and did the same. I had my wife mark sack A and B and keep the post its. I shot 2 groups from sack A, cleaned the rifle and shot 2 groups from sack B. I did that with a 30-06, a 7-08 and a 22-250 (H380) and none of the groups improved with magnum primers that I could see.
I've heard that you need magnum primers if you hunt where it gets really cold. I've hunted where it gets cold enough that the pee can in the tent would freeze at night. And I used standard primers in a 30-06, a .280 and a 7-08 and they worked fine. If it gets much colder than that, I ain't gonna be there.