My 45 ACP bear load was a 260gr. Speer HP driven by 11.9gr. WW 630 powder. The vel. From my Wilson 5" bl. was 960fps. It would shoot into 2 1/2" for 5 shots at 50yds. off bags.
I don't think the Webly can match that.
I also experimented with 300gr. FN'S with 7.7gr. Blue Dot for 770fps.