That’s an awesome issue, Ted. I’m not sure. Here's a couple examples of what I’ve heard in numerous sites over the Federal 210 vs Federal 210M variations: I've been reloading for over 35 decades and possess routinely switched involving Winchester, CCI and Federal ( I acquire whichever is on sale) https://emiliogczvj.luwebs.com/32475617/top-guidelines-of-federal-primers-small-pistol