I've used case head expansion a few times on rifle cartridges to estimate pressure. Don't know about others but all I ever used is micrometers because I had to measure repeatedly into ten thousanths of an inch and my calipers just are not that good. If you should end up using micrometers (and if they are new to you), I suggest you get somebody to show you how they are properly used. My dad was a machinest and taught me how. It's not hard but a little instruction makes a big difference when measuring those super small distances. Hope this is of some help. Maybe somebody had more to share than I do.
Bill M, FYI what Contender is referring to as a "blade type micrometer" is one with the anvils ground to narrow blades, used, for example, for measuring the diameter of a groove in a shaft as might be used for a retaining ring.
Contender, the procedure is described in Veral Smith's book "Jacketed Performance with Cast Bullets," on pages 84-86. If you don't have this book, it is highly recommended. Veral's wife Judy still has a few available (at least she did last month when I received my copy). The price is ฤ and everyone recommends adding something extra to help out Judy right now. The address is: Judy Smith, HCR62 Box 145, Moyie Springs, ID 83845. More info is at: www.sixgunner.com/FAQ/lbtbook.htm
The micrometer Veral shows in the illustration is just your garden-variety 0-1" micrometer, whatever you have as long as it still works OK. Calipers, however, are not repeatable enough as you need to measure to 0.0002".
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