You can also work with 45 Auto Rim brass; it is perfect in every way except for the tiny fact of that wonky rim.
If you have a little lathe and a drillpress, it's not hard to make a hollow punch which will FLATTEN that Rim down flush to your work surface; after that it is an easy and quick job to thin the rims to spec.
Presto! You have perfect .455 Colt brass...... which works fine in any large-frame Webley.
Jethunter (on this forum) makes great bullets for these: nice and soft, won't crap up your bore.... and accurate.
Once you have everything, load up a batch (to 455 specs, mind you!) and go find a Tank to hurt! For stopping power, by the way, it scores 74 on the Hatcher Scale: ABOVE the fabled 45ACP.... and still comfortable to shoot!