I've had some early Ithaca NIDs that were over bored -- Super-10 .790", 12-gauge .744", 20-gauge .629" and 28-gauge .570". The NIDs I have that are from after the cocking indicators were dropped circa 1935 are right on industry specs. My sample is certainly not enough to be scientific. My 1910 NIG is actually a bit tight at .724".
Wonder what Uncle Bob Edwards secret was --
Uncle Bob Edwards, Field & Stream, July 1907.jpeg