I was wondering about the caliber and the model of Weatherby. Pac-Nor, which I recommend, only makes Weatherby pre-fits for Mark V's, Vanguard's and Weatherby Light Rifle. Not too up to speed on Weatherby rifles but I recently got a Pac-Nor, 28", Savage pre-fit, Varmint contour 1-9t, 5g, in .300WinMag. Excellent barrel!
Bought the go gauge from SSS and put the barrel on at my kitchen table. Shot it about 10 times, took it back off and used a Ryan Mantha finish reamer on the chamber.
I'm running the 215gn Berger Hybrids at 3045fps and an OAL of 3.73'-ish. Much better than the SAAMI chamber.