Actually, with one make of belted brass I have seen .020" of case expansion on the belt with FACTORY loads. This brass is obviously a lot softer than some others, but it held up fine.
It is true that case heads expand more on the first firing than on subsequent firings at the same pressure, and belted case heads tend to expand more than non-belted case heads. It also appears to be true that some people don't understand how or where to measure case head expansion, and given the knowledge to do so may lack the dexterity.
The truth is that 0.020" of actual case head expansion, correctly measured, on once-fired brass, is indicative of a problem, and most likely extremely high pressure.
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