Re: 25/300 Win Mag Dies
Blygy, I don't have a 25/300WM, but several have reported that the case capacity is about 88 grains, and they get around 4,000 fps with the 100 grain bullet. I would have thought that around 3,800 - 3850 fps would be more realistic in a 26 inch barrel.
Although the 300WM case is about .060 longer than the 257 Weatherby, it is about .015 smaller at the shoulder, so the
capacity is very similar.
I am currently using 300 WM brass to neck down to 257 Weatherby as I have found the Norma 257W brass too soft. The new Norma 257 Weatherby brass is about 87.8 grains compared to 85.2 for the new 300WM brass when necked down to 257Weatherby. So the brass is obviously thicker than the Norma 257W.
I believe that the case capacity of the 25/300WM is best suited to bullets in the 115 - 142 grain range, and would choose a 9 twist barrel for bullets up to 130 grains, or a 8 twist barrel if I was going to use the 142 grain Wildcat ULD.
Good luck on your project. Brian.