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You are dealing with a process that can potentially KILL you..."
Well, it IS good to know OAL within a certain window of accuracy, but being "off" a bit is really unlikely to get anyone killed so that's an exageration as it's stated.
Witness: Virtually no one had ANY kind of precison calipers prior to maybe the late 70s. Before then we worked out our OAL with simple trials until our ammo fed and chambered reliabily. In fact, few of my generation even bother to look at book OALs today.
Until maybe the late 70s many reloading data sources didn't even have "OAL" suggestions. Those that did never worried about today's sweats over supposed tiny variations for specific bullet brands and versions of the same weight. Very few of us who died young did so because of reloading accidents.
"(NOT a cheap electric one from Harbor Freight, I bought one, and it kept going out of calibration), "
I not only reload but do a little machine work. I have several 6" calipers; a Swiss made professional grade vierner from 1969, two dials and a digital from Harbor Freight Tools from 1996, to as recent as 2005 for the digital. I've had absolutely no problems with accuracy or calibration from any of the Chinese made calipers and the costs were astonishingly low - that's part of why they are so easily available today. Those sold by our various reloading companies, usually at much higher prices, are exactly the same as HFs other than the name tags and some colors.
HF will replace anything they sell if it fails during the warrantee period, I don't see how that can be faulted. Anyone thinking a failure in ANY electronic device is indicitive of the whole brand is wrong. Anyone thinking occasional failures are unusual doesn't understand electronics and is going to be disappointed by them quite often.
Valid reloading warnings can be good but over-stated warnings lose credibilty and become meaningless.
