A good vernier caliper is readable to 0.001", and there is very little to go wrong with it. It's just not that easy or quick to read.
Dial calipers are just as accurate, when well maintained, and much easier to read. Once the rack and pinion are contaminated, accuracy goes out the window and you can do some real damage to the tight tolerances. Mine was fine for over 40 years, until I spilled some powder on it (Unique, I think). That stuff is like chewing gum once it's mashed between gears. I had to disassemble it, clean the rack and pinion in an ultrasonic bath, and re-assemble it. That's a trick, because the pinion is split and the halves spring loaded. Then it's trial and error to get the right tooth on each to mesh.
A digital caliper is even more accurate than a dial, and there's hardly anything to go wrong besides a dead battery. I bought a good one, Mitutoyo, which was not cheap, but well made. It's probably overkill for reloading, but I was an engineer for over 30 years, the last three in Metrology. Old habits are hard to break.
It takes skill and practice to use any precision instrument - including straight and with the right feel. Good calipers are stiffer than cheap ones, and work a lot more smoothly. That said, bullets aren't as critical as bearings.
