Re: heavy 257 weatherby
BLYGY, To help you work out the magazine length required with the 257 Weatherby. The bullets listed below has the following overall lengths if they are seated with their base level with the base of the case neck:
115 grain Nosler BT (1.204) - 3.436 inches
125 grain Wildcat ULD (1.268)- 3.500 inches
130 grain Wildcat BCFBHP (1.220) - 3.452 inches
I found that my Shilen 24 inch 1 in 10 twist barrel on my 25/06AI stabilised and shot accurately the 130 grain Wildcat BCFBHP, and also stabilised and shot reasonably accurately the 125 grain Wildcat ULD. Next time I would order a 1 in 8 twist barrel for that gun so that I have the ability to use bullet weights up to an including the Wildcat 142 grain ULD.
You might be interested to hear that several weeks ago I conducted an experiment, and found that my custom 257 Weatherby (no freebore) when using new Norma 257W brass in my Krieger 26 inch 7 twist barrel barrel was only 75 fps faster than my 25/06 AI (Remington brass already fired 9 times) with a 24 inch barrel.
So if you allow about 50 fps for the extra 2inches of barrel length of the 257W, I gained about 25 fps for the extra 19 grains of case capacity over the 25/06AI.
The experiment showed that Norma 257W although consistent is soft, and wont safely handle the pressure that Remington and Winchester cases will do.
I subsequently purchased a bag of 50 300 Winchester Magnum cases (Remington brass), necked them down and formed 257W cases, and then neck turned to get the proper clearance. These cases had a capacity of 85.2 grains compared to the 88.3 grains of the new Norma 257W brass, so they are obviously thicker. After their first firing it appears that they will probably produce an extra 75 fps at maximum pressure over the 257W Norma brass, but I will fire them several more times to confirm this.
Hope that the above information is of some help. Brian.