Any case head seperation I have experienced was with belted magnums. Just below the sizing ring at the top of the belt. Easy enough to see them starting to go with a magnifying glass. Larry Willis sells a die that will all but eleminate that problem designed for belted mags. I don't shoot my mags all that much, used for hunting only so I never felt the need to buy one. I noticed once I controlled the shoulder bump back to less than .001 I was able to get as many as 8-9 firings. Their not real hot loads either, so that helps too!