British gunmaker Anderson Wheeler announced their replica of the Webley revolver earlier this year, called the Mk VII, re-engineered to be safe to fire .357 Magnum cartridges without stretching the top latch to being useless . Initial release date was announced to be in May this year.
http://www.andersonwheeler.co.uk/revolver/Mark-VII
I...I kind of want one. But considering Anderson Wheeler is in the luxury gun market, I'm sure the revolvers cost a small fortune. Their shotguns retail for about $18,000, which is inexpensive only when you compare it to Purdey or Holland & Holland or Fabbri.
Don't know about Swedeistan, but here in the United State it would be cheaper and more practical to find an functioning original Webley breaktop, and set yourself up to handload .455 for it.
Just my opinion. A modern breaktop in a larger caliber is one of those things that would be cool if it could be pulled off, but it probably can't be done economically and wouldn't have any advantage over modern designs.
(And come to think of it, I've still not heard ought of the
Remington R51 re-re-release....)