This is an older thread, you might not receive a response, and will be reviving an old thread. Be sure to consider creating a new thread. I would not fret over the primer blend. There's not that much tension difference between a Magnum primer and Regular. I've tried using interchanging https://andersonfbtli.mybjjblog.com/federal-215-large-rifle-magnum-things-to-know-before-you-buy-44649654