@ 03:53 am (GMT)
Paul LevermanHamish brings up a good point. I know my cordless drill is nowhere near accurate or true. It wobbles like crazy, mass produced, planned obsolescence. Good for polishing, cleaning, and I do use it with my primer pocket cleaners, but at a very low, controlled speed.
I also had a set of electronic verniers that were affected by fluorescent lights. The closer the proximity to the light, the weirder the reading. Gotta love warranty.
And yes, it is nice to shoot off of jean covered, sand filled ziplock bags, and outshoot the mega-dollar lay your gun here strap it in and pull the trigger type rests. It's actually quite entertaining to watch how much that rig jumps around.
As to an exact measurement for length, I have used re-formed 2.5" magnum brass of various calibres in my Norma. They are sometimes quite a bit short, enough that you could use a tape measure to check them. There doesn't seem to be an issue , so far. (Heavy on the "so far".) Again, I think the concentricity is more to the point.
I am not familiar with Kincrome tools. Back in the last century when I was buying tools, I was told that when buying micrometers, anything would do, as they all use the same thread for the spindle. However, I was also told that verniers were hit and miss as to the accuracy, and to buy the best you could afford and then continuously upgrade. If you know anyone in the machining trade, see if you could check your verniers with their 1" and 2" standards. Chances are they will do it for you. This will tell you real quick what level of accuracy your verniers have.