Quintus, I had two of those rifles, years ago, and I shot factory ammo. I sold one to a friend that killed a lot of elk with it using the Weatherby 117g bullet. I don't know if that bullet was made by norma = ornx or was a Semi point partition made by Nosler.
The 117g Sierra flat base that is a semi-point stabalizes in the 12 twists at 3300, I know that for a fact. The 117g Flat base is discontinued, but there are still some floating around. The Easy button is a Hammer or TTSX bullet in the 80ish grain weight.
When those 12 twist barrel is shot out, I would surely replace it with a 26" 9 Twist where the 115g Bergers & 110g Accubonds will be doing 3600 fps or an 8 twist for use with the 133-134g bullets depending on how far you shoot. Pac Nor has a short freebore reamer, and their three groove barrel is shooting the 100g TTSX at 3850 and 115g Bergers at 3600 with a zero freebore reamer. Groups that Pac Nor barrel is shooting with both 100 and 115g are sub 3/8". Heavy bullets did not exist when this Pac Nor barrel was chambered.
The 257 Weatherby was Roy Weatherby's favorite cartridge for a reason.
The 117g Sierra flat base that is a semi-point stabalizes in the 12 twists at 3300, I know that for a fact. The 117g Flat base is discontinued, but there are still some floating around. The Easy button is a Hammer or TTSX bullet in the 80ish grain weight.
When those 12 twist barrel is shot out, I would surely replace it with a 26" 9 Twist where the 115g Bergers & 110g Accubonds will be doing 3600 fps or an 8 twist for use with the 133-134g bullets depending on how far you shoot. Pac Nor has a short freebore reamer, and their three groove barrel is shooting the 100g TTSX at 3850 and 115g Bergers at 3600 with a zero freebore reamer. Groups that Pac Nor barrel is shooting with both 100 and 115g are sub 3/8". Heavy bullets did not exist when this Pac Nor barrel was chambered.
The 257 Weatherby was Roy Weatherby's favorite cartridge for a reason.