I made myself a similar setup.It uses an inexpensive Enco or similar granite comparator stand with a travel indicator.Mine uses a datum bushing that attaches to the indicator stem ,so its a Hornady lock n load type bushing.
The setup on the link has an intetesting adjustable 3 point plate to register on the datum.Looks fine to me.
For the price,you get on tool that will handle eveything.And,its efficient to check a number of samples.
The RCBS Precision mic measures the same thing,but a different way.Its a mic head with sort of a chamber inside.You take it apart,put in your fired brass,get a reference measurement,take it apart,size,put it back in,check the amount of change.
I think one RCBS mic will cover a family of cartridges,like perhaps 308,7-08,.260 or 30-06,270,but they are $35+ each...so,I would vote for the comparator stand.
The Hornady lock-n-load setup is workable.It accomplishes the same thing as the comparator stand,but it is a clamp on accessory for calipers.I think,while it is workable,it is a little more clumsy/variable than the stand.
Once again,back to the bushing gage,if you have the indicator/comparator stand setup of some kind you can drop your brass into the bushing,and put the bushing on the comparator stand case head up.The indicator reads on the case head.I would call this the best setup(though,beware,your brass must be trimmed shorter than max or it will protrude from the bushing gage on the neck end)
There are any number of ways to accomplish this,depending on the tools available.
See if this link works http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
It is a granite comparator stand for $29.Can you see how you could slide a bushing type case gage under it?Go to the catalogue page and there are options.An SPI stand with an SPI indicator is just over $100.
SPI stands for Swiss Precision Instruments,its a pretty good line of tools.I would expect a Chinese,Harbor freight grade tool for $29,and better quality from SPI.The $29 stand will work for reloading.
More than one way to do it.
I have used a similar high precision setup to measure very close tolerances in industry.Its commonly called a Swede gage,the indicator measures in ranges of millionths of an inch,and is calibrated with Johannsen gage blocks.When parts must be held to tolerances in the tenth of a thousanth range,it is the tool to use.