The British revolvers were chambered for a cartridge identical in the cartridge case with the .38 S&W. There is no .38 S&W "short" or "long", only one size.
The Webley MkIV in .38 was used by both the British military and by police forces around the world, but it was not the standard revolver of WWII, the Enfield revolver was. While similar, they are not identical and the insides are quite different. Both Enfields and Webleys are available and show up fairly often at gun shows. Both are collectible and also practical pistols, though the .38 S&W is not considered a very powerful cartridge. (I note that none of the folks who make those statements volunteer to be shot with any of the cartridges they denounce as useless.)
The Webley .455 (MkVI) revolvers were made by Webley and also by Enfield. The conversion to use .45 ACP with moon clips was done by American importers when the guns were sold on the U.S. market, since .455 ammunition was scarce here. Unlike the Colt and S&W Model 1917 revolvers, which need clips only for extraction*, the converted Webleys will not work without moon clips, as there is no sharp shoulder in the chamber to support the case.
Some people have (with patience and money) obtained .455 cylinders to convert the old guns back, but it is not easy.
HTH
*Yes, I know about the early Colts, but this is a general response.
Jim
