50 WSM sizing die?

I remember Noveske building a Winchester Model 70 in 4 what he called 458 Noveske (300 WSM necked up to 45.) Naturally this was before he died in the car accident but he stated that he thought it would duplicate 458 Win mag performance with equial barrel lengths. What do you intend on doing with it? Bullet selection is much better in the .375 and 45 calibers than the 50s.

Makes my shoulder sore just thinking about it.
 
We are pushing 647gr .50 cal bullets at 1350fps. HOG killer. I`ve been using a RUM full length sizing die to get the taper needed but it aint quite right. The reason for using 50cal bullets are they are so cheap. 500 bullets for $140. Also use Barnes 647gr x-bullet and Lehigh subsonic brass bullet with .243 bullet inserted in the hollowpoint.
 
Here is the 662 gr. API moving at 1,375 fps. Next to it is the Lehigh Subsonic hollow point with a Hornaday 6mm 87 gr. V-max payload bullet, giving a total weight of 775 gr. moving at 995 fps.
DSCN4037_zps28aa7722.jpg
 
Finally found the correct sizing die. I called CH4D and they had one in stock but it`s under a different name. Thats why I had a hard time finding it. This is one of the most fun rifles I ever shot. Vestal`s Gunsmithing & Custom Rifles built it. They have the reamer and brass for this cartridge.