In fact nominal size for a 16 gauge bore is .662" or 16.8mm. At .677 that bore was actually .015" oversize. At one point L C Smith bored their 16's to .650" or .012" under nominal. Later on they changed to the standard .662", with I presume a bit of manufacturing tolerance.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra