As I stated, if you believe that a set of springy calipers are accurate to read .0005", then go right ahead and do it that way. I will GUARANTEE that if I measured those same cases with my blade MICROMETER, it would read EXACTLY what your belts measure. Why you need the accuracy of .0001", is so you can read to EXACTLY 1 10, 000th of an inch, you simply cannot do that with calipers. PERIOD.
I have measured case head expansion for many years, no where, anywhere, in no manual does it state to use calipers of any type to measure case head expansion. I am a machinist, I would never use calipers to read ANYTHING once it had been turned/milled to size, inside/outside mics that read to .0001" are mandatory. Calipers only ever get used for ROUGH measurements, because they are inaccurate by nature.
Getting to brass expansion, .0005" is a generic measurement that equates back to the days of copper crusher testing, as brass is harder than copper, the deformation of brass is less, it was guesstimated to be less than the amount of expansion it took to expand a primer pocket for 3 firings before case hardening proved that no more expansion took place. It has no exact correlation to the pressure the cartridge is producing, because brass hardness varies, soft brass, such as Federal, will deform at much lower pressure than harder brass like Winchester.
I concede that brass deformation can be used to ascertain safe loading techniques, but it does NOT tell you what pressure you are running, neither does the chrony reading. All it tells you is the brass is expanding at those pressure levels.
New brass often expands twice as much, or more, as once fired brass, is this excessive according to your calipers?
BTW, new unfired brass should NEVER be used for case head expansion measurements due to the very fact that it always expands far more than once fired brass, and brass should only be used for case head expansion for a maximum of 3 firings.
If this is not what you wish to hear, then it's too bad that you can't learn the correct methods, telling me I'm incorrect doesn't change the facts that YOUR methods go against everything ever written on the subject.