To not hijack this thread but a buddy of mine that produces ammunition implies the Federal 210M primer. Why, I have no idea as he was attempting not to offer me proprietary info. I will use the Lee Hand Priming tool when I get all around to using the Feds. https://215federalprimersforsale94825.bloggosite.com/38546118/the-5-second-trick-for-federal-large-rifle-benchrest-primers