Yes! You would have to drill out the larger bore barrel very carefully and insert a liner in the caliber you desire and chamber the liner. Re barrelling to the new caliber with a whole new barrel in the new caliber would be greatly much less costly and quicker and more reliable. The first process is done in guns where the markings on the barrel need to be preserved. Otherwise, silly.
Any good gun smith can get a barrel of the quality you desire and chamber it and install it. Cost varies first with the quality of the barrel and then the overhead of the work shop.
.240 Weatherby is basically a belted case 6mm / '06. Fairly easy in a gun already '06. I believe the .300 Win and .257 Weatherby use the same head/rim, again, rebarrel, no problem. As I recall the Weatherby is a bit longer. How long is the original action? Ask around at the range. Many men with machinist training do this sort of thing in the basement or garage. Luck.