Thanks for that explanation, JE. Interesting stuff. Hard to imagine primer pocket getting tighter with subsequent firings, but if you say so, I'll believe it.
Reloader have for years made this stuff up. I woke up one morning to find while I was asleep some bench rester decided the case has head space. No one knew what he was talking about. This revelation did not complicate my life because my cases do not have head space.
And then there is the part that makes reloading unfair, 'it' does not happen to everyone. I like to start 'even' or on a level field. I have purchased rifles that were sold to me as being 'suspect'm I purchased 4 rifles for $25 each thinking I could build 2 rifles, I thought they were talking about the barrels because all 4 were shot out/cut out with hot high press metal cutting has.
That left the receivers, I tested all four receivers with one bolt and barrel. A kind man in Arizona suggested I was into some scary stuff. I test fired all four receivers and found nothing that I thought was suspect. Thinking the Arizona smith was correct I called Hodgdon; I informed them of my plan. They had no problem but warned me about my plan, they said there was a possibility my case forming loads could become over max after the cases were formed.
Level field: The case head expands when fired, no one agrees but my factor over the counter new ammo when fired has a case head expansion of .00025". Who measures? If I load the once fired cases and measure before and again after I should expect a case head expansion of .00025". When reloading these cases I want the same amount of case head expansion. If I shoot a heavier bullet or use more powder I expect the case head expansion to be greater. Moving way-ahead: I have had case heads expand .010", That may not mean much to most but the case head expansion is 40 times greater than factory over the counter new ammo.
The effect the high pressure had on the case; the case head expanded in diameter, the case head shortened from the cup above the web to the case head, the flash hole increased in diameter and the primer pocket increased in diameter. And the primer just fell out.
Convex / concave:
My rifles have case head protrusion, my chambers have clearance, clearance is the difference in length between a go-gage length chamber and a minimum length/full length sized case from the shoulder/datum to the case head.. And I wonder how could a primer pocket reduce in diameter when being fired?
F. Guffey
