If any material was removed from your 2e, it was most certainly on the ID of both barrels from the cones to the depth your Skeets bore gauge will reach (about 12") or perhaps a bit further. As your Skeets enters fromn the muzzle end to the same depth and you're getting .718-.719 ID in that forward area, you have surveyed ID except for the midway 4" of length. Be interesting to know the nature of the bore wall in that transition. Is a step? A taper? As to what the indy balls do on a bore gauge, they are ALWAYS compressing against their springs while in the bore relative to their "free" diameter outside the bore. I also am confused as to the relevance of the mechanical principle of the gauge and its influence on or received influence from bigger or smaller bores. It simply measures one thing or another. It will "measure" absolutely when indexed to a standard (the .700 ring gauge) or, in the case where relative choke constriction is all that is desired, it simply "counts" reduction in diameter in 1/1000s of an inch if the bezel marker is zeroed while the gauge is inserted in the bore. Everything should be made as simple as possible, but no simpler, at least in my case. I don't know what you're missing but exit number subtracted from bore number is points of constriction of choke (reduction in ID size. As for the relevance of .730" ID back by the cones and some distance forward, you need another "assumed" hypothetical, to wit, a gun with the "major" bore pretty much adhering to one single diameter to all its length between cones and chokes. Since that hypothetical is the customary case and expectation in an unmuddled gun, choke is simply relative to the ID of the entire bore.
Hope this helps one of us understand the other, JD, but I'm not counting chickens yet. More like candling eggs.
jack
