Ed, this is one time that Google has misinformed you. 8.82 divided by 25.4 = .247244". Now add a nominal .008" for the depth of two grooves (opposite grooves of .004" depth each) and we have a groove diameter of .355". 9 divided by the same 25.4 = .35433" so .355" is quite close. Going by the bore diameters stamped on the barrels of most Lugers, I'd say they held tolerances quite tight as most I've seen are 8.81 and 8.82.
Having said that, when OTHER 9mm pistols are discussed it's not uncommon to find oversized groove diameters. I have yet to find a Browning Hi-Power less than .357" and most run .358 - .359". I've also measured many CZ-75 barrels and all of them have been .357" or larger. My own CZ-75 is .358" and it's a beautiful commercial model, deeply blued and new when I purchased it in England in 1985.
So I think it fair to say that many 9mm pistols will have oversize bores but most Lugers will not. At least that's my experience.
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