470

Your observations are indeed correct and this stems from the way bore is designated.

The Groove diameter of the 318 is .330 inches ( I have one) but bore is traditionally and correctly measeured between the lands so the .327 plus and minus quoted by some is therefore the "correct" bore diameter.

Bullet makers use the .330 measurement to make the bullets and in the past I have used both the now obsolete Goodnel bullets (.330) and Ken Stewart bullets also .330 in my 318.

Incidently I have been "hunting down" 318's in the RSA and this past December I located no less than 4 specimens all with badly oroded throats and barrels. The mercury containing primers of yesteryear sure put many a rifle out of comission.