Hoot wrote:Draino wrote:...snip... I dont know where to measure at the web area to get a correct err....whats it called, 'case head expansion?' measurement, but at the lowest point before the extractor groove, IIRC it was .503-.505 I think. I will check again though.
Can
Set your micrometer to say .5000 and slide the resized, clean case through from front to rear. If it has been shot at least once, it will drag or catch where the widest spot is and that's usually right where the web transitions to the wall. That's the area of interest. Once that area exceeds .5015 or so, you run the risk of it seizing or dragging and preventing an AR bolt from rotating into battery, depending upon how tight, or not, your chamber is. If it fails to pass at .5015, it's scrap brass. Bolt actions in theory (see sig), will be more tolerant as you can cam the round into battery with more closing effort. Best to find out which cases are going to be problem children before you load them back up. Again, this is more of an issue in an autoloader. My clean chamber seizes cases at .5017, so not wanting to have issues at the shooting bench, I toss any case when it can't pass through the micrometer when set to .5015, to allow for soot fouling after an extended shooting session.
I grade my resized, clean cases into different peanut butter jars at .5000, .5005, .5010 and .5015. When choosing which ones to reload for a project, I usually use the .5015 ones for foulers and the .5005-.5010 for keepers. The .5000 are saved for hunting rounds, where I don't want anything to go wrong.
Hoot
Sorry to say this but IMHO, measuring this dimension is a job for a micrometer, not a caliper.
Hey Hoot, could you do me/us a favor and show us a picture of your micrometer and a link to where we could order one?