Just checked a 1898 serial number 266380 at 21 and 22 inches and got .658 at 22 inches and .663 at 21 inches. This is a 30 inch barrel just marked the spots at the designate lengths. Looks like .005 taper to an inch needs to be considered.
With BR's measured example worrying the sight out with a 3/8 rod with a hack sawed split for wrapping with 240 grit wet or dry paper. Keep the paper wet with kerosene or WD 40 or some other light solvent. Maybe this would take a couple of hours. With mine example all day and a pile of paper. The older one with .030 needing to be removed several days, maybe grinding then lapping would work.
If anyone else has a couple of original and copied 1903 sights that they want to contribute to an experiment? You do need to know I am slow getting around to this stuff and it may take a month or two.
Boring these would take a day or so to make a fixture, once the fixture is in hand about an hour or less to set up. Two minutes to run one and change the next sight. The more done at a time the better.