To not hijack this thread but a colleague of mine that makes ammunition implies the Federal 210M primer. Why, I do not know as he was attempting not to provide me proprietary details. I'll use the Lee Hand Priming Instrument when I get all around to utilizing the Feds. Ken, https://winchestersmallpistolprim57890.mybloglicious.com/52457342/5-easy-facts-about-federal-no-210-large-rifle-primers-described