Boomer,
You will probably have to grind a pad to fit that Weatherby.
I have fired that rifle, in both braked, and unbraked versions. Don't care to fire the unbraked version again though. With the brake on, it's quite managable. Without it, it bites hard!
While I hate the noise, and pressure wave that slaps you in the face, that the muzzle brkes create, the .378 is one round that needs it!
Good shootin' to ya!