So from what I can gather, the cartridge was designed as an improvement over the .450 Alaskan - nearly the biggest thing that would fit in an 1886 Winchester; fitting well in a #1. It's a .50-110 necked to .475 caliber. I have now seen a couple online in the caliber, and they look like standard 1H's, but in a 26" C barrel.
Turnbull has data online. It appears to beat the .450-400 by 150 fps with a 400 gr bullet. Barnes has bullets designed for it, and I would think for reduced loads, one could run bullets intended for the .480 Ruger/.475 Linebaugh.
I had been wanting a .450 Nitro, but this one gives me pause. anyone handle one yet?
