One other point about the value of a case gauge versus a barrel. Imagine a loaded round with a substantial asymmetry near the base of the cartridge (say, an un-removed Glock bulge). If you drop it in your barrel and the bulge happens to line up with the feedramp, it will plunk. If you then put that round in your magazine and the round comes up with the bulge at the top... failure-to-feed problem ahoy! Case gauges don't have feed ramps. They are more unforgiving than most chambers/barrels.
Only you can decide whether that matters to you. But barrels are not completely functionally equivalent to case gauges.
