A 300 wby shouldn't be that hard to get to shoot accurate, I agree on what the others have posted, on checking all your mounts and action screw to see if anything is loose. Btw, the proper way to torque your action screws is on Weatherby's website, under FAQ's. I would also check the barrel crown and try shooting some loads without the muzzle break, to see what happens. I'm curious, just what factory ammo did you try and how accurate was the groups? What kind of bullets, weights, powders, did to try reloading and just how accurate was the groups? and what was they doing just like 224 king asked?
Rob