This is from an article I came across a long time ago. It's the load I use in my Antique revolvers, chambered to accept the 455 Webley.
Many antique pistols have generous chambers and will also be marked for 476 cartridges. These were from the BLACK POWDER era.
The reason they used hollow base/skirted bullets was because bores and cylinder throats were all over the spectrum. Same goes for the diameters of the bullets available at the time.
I have also used BP to load the oldest pistol, which is an RIC model, built in Belgium and British marked with pre 1898 stamps. The BP load is actually more consistent but the clean up later is a real chore.
One big mistake a lot of people make when reloading this old cartridge is they forget to CRIMP the case mouths. Some don't believe it's needed. IMHO it's critical to decent consistent accuracy.
If you're shooting the MkVI break action types, they're the strongest of the type and stronger than even the early solid frame RIC types. The strongest revolvers chambered for the round are likely the Single Action Colts and the double action Smith and Wesson/Colt models 1917.
These lovely old handguns really don't deserve to be loaded hotter than the load below. It's hard on them and you will get leading.
Solids, such as those sold by Western Metal will work well IF THEY MATCH YOUR BORE.
Some folks get very perturbed when mentioning jacketed bullets.
Due to the requirements of the Hague Convention, lead bullets were prohibited. Soooooo in 1939 they issued ammunition with copper jacketed 454 diameter, 265 grain bullets with three stab style crimps.
.455 Handloads
In my experience, my .455 Webley handloads are clean-burning and much more accurate than the available factory ammunition. For comparative purposes, I shot a box of newly manufactured Fiocchi ammunition. The average velocity for these rounds was 601 feet per second (fps). My best group with this factory-loaded ammunition
measured 2.75 inches across.
For my .455 Webley handloads, I load a .454-inch, 255-grain, lead, semi-wadcutter bullet over 6.8 grains of Alliant Blue Dot powder. I like using Blue Dot because I can use 100-percent density loads, with no airspace between the bullet and the powder. I find that 100-percent density loads burn more consistently than tiny loads of faster-burning powders that move around inside the cartridge case. I used once-fired Fiocchi .455 brass, which takes small pistol primers. This load generates a 12,600 psi chamber pressure, so it should be safe to shoot in all .455 Webley revolvers.
The actual loading procedure I use for .455 Webley rounds is a little more painstaking than my standard procedure. I use an RCBS single-stage press, and I de-prime, size and prime the brass as usual. Then I expand the case mouths and I get ready to charge the cases with powder. Because the .455 Webley Mk II cases are so short, I am very careful with the powder charge. With a short case like this, it’s easy to get into an over-pressure situation by going just a couple of tenths of a grain over the maximum charge.
To make sure that doesn’t happen, I weigh each charge. First, I set my RCBS Uniflow Powder Measure to throw a charge that is 3/10 of a grain too light. Then I use a Redding Powder Trickler to dole out a flake of powder at a time, over the pan of my digital scale, until I reach 6.8 grains of Blue Dot powder. Then I charge the brass. After that, I seat the bullets with a good, solid roll crimp.
This load has been very accurate for me. During the shooting session for this article, my best 25-yard group with this load was 0.5 inches across. Most groups were between 1 inch and 2 inches in diameter. Velocity with this load averages 683 fps, which is certainly hotter than the Fiocchi load, but it is still a mild shooting round in the big Webley.