My .577 3" 1902 Webley is mentioned elsewhere here on NE.
It was rebarreled some years before I got it, likely in the 1970's. No prior history available and sadly whomever had the rebarrel done lost or tossed the original barrel. My guess is that it was .450 or .500

The thing weighs ~11.5lbs, 28" barrel, and is quite a handful enough just with the Reloader 15 equivalent of the old 90 Cordite 650 grain bullet loading at 1950'/sec

Chris, I think a .470NE as you have acquired would be the sweet spot for a rifle like this.

- Mike