It is a normal thing to have long throats on high pressure cases to reduce that pressure. It is not the most efficient of chambers but is perfectly safe. Weatherby have been doing for years with great accuaracy and speed. As a smithy the biggest mistake I see is a new barrel chambered in a weatherby round with a short throat causing excessively high chamber pressure.
Just pick a projectile suitsble for the intended purpose, load to magazine length and test some different powder charges to achieve the best accuracy.
Oh and have fun doing it.