I’ve got a Webley MkII that was “shaved” to allow .45acp in moon clips to be fired.
I’ve found that a 200gr Lee SWC sized to .452” over 3.8gr of 700X or RedDot shoots to point of aim at 7yds. It’s also satisfyingly accurate.
It’s not recommended to use factory or factory level .45acp as the cylinders weren’t heat treated to tolerate the pressures.
Lyman made some .454” .45 molds for years. You may likely find one in one of the online auctions.
I’d first recommend slugging your bore to determine your actual need.
The factory.455” bullet is a long-nose round nose, hollow base slug. It was swaged from SOFT lead and used black powder. A cast hollow base bullet is typically a single cavity mold. Very slow to cast.
The one on the far right is a .455 Webley.
There was at one time a hollow point load called a manstopper, and a wadcutter design.
https://en.wikipedia.org/wiki/.455_Webley
Photo courtesy of Wikipedia.
(.450 Adams, .455 MkI Webley, .455 MkII