Most rifles fire properly tailored reloads better than factory fodder at least that has been my observations. I never use factory ammunition in any thing other than a 22 rimfire. If I was having problems with a new weatherby or any other brand of rifle the first thing that I would do is call the manufacturer, request the type of ammunition they used and test fire the rifle. If I still could not get it to shoot then I would check the bedding, check the crown, make sure the mounts are tight,change scope (even if I had to Borrow one) and finally have someone else to test fire the gun. If all this failed then I would contact the company that made the rifle, tell them what I had done. I am sure they will be happy to try and solve your problem. I just went through the same thing with a Savage 110 Tactical in 338 Lupua. You couldn't hit a bull in the ass at 100 yards.