Alan:
Brace yourself! I load the 650-grain Woodleigh Weldcore over 97-grains AR2208, with a saddle-felt wad to take up the space! Of course, this is not as scary as it sounds: the original load of 570-gr paper-patched lead over 167-gr BP generated 10-tons pressure, whereas my 'light' nitro load only generates around 8-tons.

The case-length is 2 3/4 inches. Most 20-bore brass shotshells are 2 1/2 inches. Are yours CBC?

I was offered an Alex Henry reloading tool for this cartridge by Clive H. in Melbourne, but in the end he sent it off to the States when 'his' double was sold there. Bugger!

It's a simply marvellous cartridge, and you have a rare bird there with your single-shot mate. Here's the yarn about my rifle, if you haven't seen it:
Alex Henry 20/.577 Story

Sorry 'bout hijacking your thread, Mehul, you can have it back now!