+ or - a thousandth of and inch. Maybe more depending on many things from the day of the week the barrel was manufactured to the mood of the inspectors and how desperately they needed the barrels.
I have a new in grease O3-A3 barrel that measures .3092. It still has the packing sleeve around it, except for the muzzle where I took the measurement. The other 03-A3 I have has a .3085 bore and the low serial number O3 has such a worn bore, there isn't a lot of sense in even bothering to measure it.
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