Originally Posted by
mdi
I wouldn't for a couple reasons. First it's digital. I started using micrometers as a machine operator a couple years after I got out of high school and used a plain Starrett 1" mic. I used it steadily for about 12 years (daily) until I bought a Mitutoyo, again a 1" "standard mic. I used these to measure machined parts down to .0005" (learning to use a mic with a vernier type scale is simple and the "feel" is soon established). In all the time I used precision measuring tools I haven't found any digital type to be as reliable as a plain "analog" mics., and I like to see the hash marks lining uo rather than some numbers that "randomly" show up on a readout. (life long machinist/mechanic). If I were to recommend mics I'd say the ones sold by Lyman are as good as needed for reloading and will last many, many years if cared for properly. (I got a "Lyman" 1" mic after my good tools were stolen and it is accurate and working quite well after about 15 years use for reloading).
There are lots of hints to measuring an odd groove slug, but I have used two. First is using a sheet of shim stock (.002" is about as thin as can be managed easily) and wrap the slug and measure. Subtract twice the thickness of the shim for the slug diameter (if using .002 shim stock, subtract .004" from the measurement). I've been using mics for quite a while and I developed a good feel so I am able to measure odd grooved slug directly with good accuracy; I can slowly close the spindle on the slug while I am turning it and I can get an accurate measurement by feeling the slug as it is being turned in the mic. I think if one learns to use a mic good enough to get no more than .001" variations in their measurements, that's good for all reloading measuring chores.
Jes an old phart's opinion/experience...