Here is my .500 - .450 No.1 2 ľ” double rifle again. It is Birmingham made and proofed pre-1887. Marked and retailed by A.Robertson & Son, Wick, Scotland. It has a H.Homer, Birmingham, patent foreend latch and non-rebounding locks.
I once found a set of RCBS dies on ebay. My hunting load up until now: Cases resized from Bell .500 NE or Hornady .470 brass, CCI LR magnum primer, 70 gr VV N140, open cell foam wad 25 x 14 mm, 350 gr Hornady rn, for 585 m/s = 1920 fps. One problem: The .500-.450 #1 had a thicker rim than both the .470 and .500. Such “thick rim” cases are not available afaik. Graeme Wright suggests several solutions to the problem, but I invented another one: I took the extractor out of my rifle and applied a drop of silver solder to it’s rim recesses. Some carefull work with a Dremel followed. Now the cases are held back against the breechface by the extractor, no excessive headspace.