I wouldn't say that anyone who thinks one of those drop in, brass shoulder gauges "tells all honestly" is very savvy at all. You don't need to set the ring on a dial-type bore/choke gauge in order to measure constriction. However, the drop-in gauge only tells you constriction based on standard bore diameter. Anything differing from standard--and I've read bores that differ close to .020 from standard--will give you a totally inaccurate reading.