I think what they're getting at is if you snug down the barrel against the bolt, that would be right on the measurement of the GO gage. When you tighten the barrel nut, it will take up a (very small) certain amount of slack in the threads between the nut, the barrel and the receiver, which typically 'pulls' the barrel forward 0.001-0.002"... which is right about what they described.
GO/NO-GO gages are generally the best option. If you do it as described above, the bolt handle should even begin to close on a NO-GO gage, which is a good safety check just in case. If you do use tape, try using something a fuzz thicker like masking tape - typically 3-4 thou thickness, which is about the difference between a GO and a NO-GO gage.
If you don't already have 'em, you really really should get some sort of comparator for measuring cartridge headspace - mainly for use when setting up your sizing dies (I recommend either the Hornady LnL tools, or the Sinclair inserts if you can swing the $$$). It will also come in handy when checking the relative dimensions of your GO & NO-GO gages (or whatever substitutes you end up using).
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