For many of my cartridges I just invert a 40 S&W case over the case mouth. The length of the whole shebang is my reference number. I size the rifle brass and check again with the "40 gauge." The difference in the lengths is the amount of shoulder bump.
I do this with some cases but use a shellholder. Shell holders have a big enouph hole that it fits 6.5 and slightly bigger calibers. Works great! For checking headspace I'll measure a new piece of brass than use .5 thou scotch tape on the head of my bolt until I get pressure closing the bolt. My new rifle I just put together headapaced 2 thou with new lapua brass.
