How long is the barrel? My prohunter barrel was too thin to cut and thread til down to about 20 inches and I didn't want to give up that much velocity. Mine liked 150 to 165 grain bullets generally and H1000 and RL19 for powders. Standard 25.4 inch factory barrel.

My favorite loads were

85 grains H1000. 150gr fail safe. Fed 215 primer. 3250fps.
84 grains H1000. 168gr ballistic silvertip. F215. 3100 fps.
75.6 grains RL19. 150gr Hornady boat tail spire point. F215. 3200 fps.