That’s an awesome concern, Ted. I’m not sure. Here's a pair samples of what I’ve read in various places to the Federal 210 vs Federal 210M distinctions: I used to be looking at the cabela's website, one particular critique claimed you could not use federals within the Lee auto primers. https://210m-federal-primers21852.iyublog.com/31193383/rumored-buzz-on-federal-primers-gm210m