I originally posted this in the Wheelguns, Pistols, and Handcannons forum but realized it should probably better reside here, as the thread deviated from covering the Webley pistol more to making of the brass for it.
Having recently acquired a Webley Mk VI and wanting to reload for it, I bought a set of Lee Dies and a Lee Factory Crimp die for 45 Colt (that was previously listed on their website as also working with the 455 Webley Mk 2, but more on that later) and went looking for empty brass. Whoops, none to be found except very expensive Bertram brass at $2/each from Midway.
Numerous threads talk about converting the .45 Colt case by trimming the rims (and length), so I made a few that way using the "chuck one in the lathe and thin the rim" trick - which worked, but I thought it to be way too labor-intensive. After thinking about the problem for a while and figuring there had to be a simpler way, I came up with a swaging die that reduces the thickness of the Colt brass without removing any metal, and at the same time facilitates cutting off the excess length.
Referring to the attached diagram, the die is a simple affair that's intended to be used either in an arbor press or with a hammer. Basically what it does is swage the top/forward surface of the Colt rim, which is nominally .060" thick, reducing it by .025" down to .035", which is the maximum thickness for the 455 Webley. The diameter of the rim increases somewhat, but doesn't seem to interfere with loading in my Mk VI.
The depth of the "step" in the die can be adjusted to yield whatever rim thickness works best in your Webley, but given their age, I'm guessing most would favor the maximum.
The way I use the die is to insert a sized 45 Colt case, place it mouth up on a smooth steel plate, place a half-inch socket extension over the exposed case and hammer it until the bottom surface of the die contacts the steel plate. (I'd use an arbor press, but don't have one...) Then I cut off the excess case at the top of the die, remove the case and trim it to .760" in a case trimmer, and finally chamfering the case mouth. Goes faster than the time it takes to talk about it.
I've loaded, fired, and reloaded a bunch of these cases already, using the data that came with the Lee dies, and all worked great! So until Fiocchi makes another run of .455 Webley, or Starline starts making the cases (they told me they expected to make them this year - 2015!) I'll be punching mine out from 45 Colt cases.
My die turned out a bit rough since I'm not a professional machinist, so I don't intend to make any more - please don't ask. Feel free to take my drawing to your own machinist if you want to have one made, or make your own if you have a lathe.
Bud