I don't have a Winchester, but bought a Rem Model 7 in 300WSM last year. I'm still working on loads for it. The Hodgdon and Barnes web sites give loading data for this caliber. Currently, I am using Nosler 180 grain AccuBonds with 63 grains of H 4350, Federal brass and Winchester mag rifle primers. I'm getting good groups, but not yet the consistent sub minute that I think this gun will do with the right "Tweeking." Let me know how you are doing with this.