Primers matter.

I had groups go from 1" to 3" from just changing primers.

I've also had point of impact move a full foot at 100 yards while maintaining excellent accuracy from just changing primers.

As for velocity, sometimes the difference is minimal, other times it's closer to 100 FPS.

The only way to know for sure is to ask your rifle.

You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.

You cannot over estimate the unimportance of nearly everything. John Maxwell