I think you'll find that most standard contour barrels will measure about .650" at the muzzle, while bull barrels will measure .750" to .800" at the muzzle. I just measured a .270 standard @ .650", and 3 bull barrels at .750"(22-250), .775"(.243) and .800"(.204). I would expect the larger bores to have heavier contours and larger muzzles too, like .44mag, 45-70, etc.