Jerry,
Your concerns are appropriate. That does not necessarily mean that the data collected by a "hobbyist" is invalid, less accurate or useless.
Having been around the metrology end of the biz a little as well as various types of test setups, I can see where the "repeatable standard" matra could be applied in more than one way. For example: Joe, the hobbyist, buys a strain gage calibrated by a manufacturer that produces them for many industries and produces high quality and reliable strain gages with calibration traceable to national standards. He then uses industry proven methods of measurement of his barrels using measuring devices traceable to national standards. Can he get acceptable data? Does he need to put a direct reading pressure gage on the barrel that has a traceable calibration to national standards? IMO, he's met requirements commonly used in many industries. Sure, some could be more stringent and require yet another level of the overall system to be calibrated, but I would say it's as likely as not.
My direct experiences suggest that having measurement methods/equipment traceable to national standards is good, but it doesn't guarantee a good measurement. I think you'll agree that there are other factors that can affect the outcome of measurment besides calibration of equipment in complex applications.
Bill used a strain gage and likely the micrometer or other measureing device that was traceable to known standards.
So, I think it's unfairly dismissive to suggest Bill's equipment and data is either inaccurate, unreliable, not applicable or invalid, as I don't believe there has been enough information shared here to make that determination by anyone. As to "statistically significant" quantities of tests, I dunno, I didn't note whether he tested one or some other quantity of a given load. But like many electronic devices of today, the device is probably more sophisticated than the elaborate setups to gather similar data many decades ago. It really does have tremendous capability. How the data is applied is no less important than the instrument used to collect it.
