I've had two of the Howa 300WM and both were exceptionally accurate. The current one has a muzzle brake as a consolation to my aging joints.
I'll tell you flat out that it takes a much moretalented shooter to get good groups with a hunting weight 300 mag than with a 308 or 30/06. Recoil becomes a big factor and recoil attenuation even bigger. I used to shoot a 300WM target rifle and have seen what happens when the shooter fails to hold exactly the same for each shot.