Case Head Expansion
Posted: Sat Aug 25, 2012 10:56 pm
Hoot, I love this picture of your's. One reason is that it amply shows the measuring area, for case head expansion, which for the uninitiated is the shiny area about .200" north of the rim, about .100" north of the top of the extractor groove, at least that's where I measure mine.
Question: I read that primer study from James Calhoon you site and it has some really good stuff about primers. Did I read correctly, he seemed to be touting, the case head measurement area, to be exactly north of the extractor groove, the area that actually touches that groove, but is on the case body???
Taco, which area were you measuring the .003"-.004" expansion, using 1680 and those 350gr Interlocks? I assume you did a before and after comparison, correct? As I do my measurements, 3-4 thou is allot. Can you describe your methodology?
Lemme just say that measuring case head expansion is poor at best, for reading pressure signs. If for no other reason, the lot to lot changes of brass composition, throws the reading out of the window. Having said that, I keep track of the numbers, all the time, but I do so, by lot numbers. Poor as it is, case head measurements, I still find it useful..
..t