If your getting case head separations, it isn't the brass it's your prepping technique. Brass won't separate if it fits the chamber. All manner of maladies can beset brass but case head separation isn't one of them if it fits the chamber. If loading the same caliber for different rifles I either set the headspace to each rifle with the same gauge or have different dies or different shell holder(ground to the correct headspace) for each rifle and keep the brass separated by rifle.
Over the years (60 yrs of reloading) I've found that running your pressures so close to the ragged edge that you start opening primer pockets aren't that advantages, slowing your load slightly or changing powders will get you the same accuracy. Opening primer pockets isn't very far from blowing primers and that can cause some serous damage. Yes I've opened primer pockets and have blown primers but try to make sure it is something I can avoid..
As stated above, case head separation can be caused by over-working your brass; that is bumping shoulder a bit more than necessary repeatedly will displace the brass (requiring trimming more often than would be expected may result). This results in thinning of case and often results in a visible "pressure ring" appearing where the solid case head joins thinner side walls of the case. It can also be detected by running a bent paper clip down case wall and an indentation can usually be felt before case failure occurs.
Soft brass does not cause case separation but can result in premature case head expansion/loose primer pockets after just a few firings. Of
course, excessive pressure can cause loose primers on the best of cases.
Grinding shell holders for headspace is a new one on me.....
Generally, the reason to shorten a shell holder is due to a long chamber and/or die, which means the die bottoms out the top of the shell holder before the shoulder can be bumped back far enough to chamber the round.
Gunsmiths regularly take .010" off with no issues. You can use coarse emery paper on a flat surface to sand them down. Getting them perfectly flat is not required, as there's no reason to touch the die anyway.
You have me curious as shell holders are pretty hard. What method do you use to shave the shell holders down to keep them flat and precise?
Bought my first loading press in 1954 and it still serves as my only single stage press. Herters shell holders are a bit softer than others and a bit thicker, not to mention almost impossible to find today. This proved to be a problem in bumping shoulder sufficiently used in conjunction with my set of RCBS dies. Faced the shell holder off in the lathe to resolve the issue.
Have run into the problem on one or two more shell holders of various makes since I sold my lathe and, while not necessary to hold 100% true, found that the drill press serves well (to save burned fingers)
just grind the head down on a 1/4" machine bolt as shown & use coarse emery cloth on a flat surface.
Regards,
hm
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