This is why I bought those te/me gauges years ago and sold them off, my opinion is whats at the muzzle cause I was getting false or worn readings for te, having bought two of those gauges before I figured out they were both giving the same reading.
Nah, I go by visual observation only on rifles I want to buy or evaluate for resale out of my collection, you can get a pretty good idea looking at the rifling wear and the muzzle, making sure there aint obvious damage at the throat.
I haven't seen any te gauges for mauser rifles for instance, always seems to hover around american firearms, but wait, that's where all the money has been, so the gauges give the uninformed a false sense sometimes of bore wear when reselling so someone like myself can pick something up for a decent price with a, ummm, horrible te of 2-3, and grouping at my range sessions nicely at 300 yards.