or 475 OKH short or 470 Capstick short

Why this cartridge? – Because there is no 12mm/.475” of this class.

At the first glance the venerable 458 WinMag is more than enough for shooting 500grs slugs from a bolt action rifle. Regarding the curved trajectory of the 458WinMag one could try to get more or less identical performance (near the muzzle) by using less sectional density inside the barrel and a reduced powder charge. One result of course is an even more curved trajectory which is less important for the intended range of large caliber cartridges. And what about having more fun with 600grs bullets?

Cases can be built by cutting 300WeatherbyMagnum brass right at the shoulder/body junction(s. Picture).

From left to right: 458WinMag, 12x59, 300WeatherbyMagnum

QuickLOAD is a well known software tool to simulate interior and exterior ballistics. Two cylindrical cartridges of same actual powder space, same bullet weight and same maximum pressure but different caliber must have a difference in velocity. Feeding these data of the 458WinMag and 12x59 into QuickLOAD will give nearly indentical velocity values. But there must be a difference. So only measured data can tell more about the virtues of this .475 caliber cartridge.