Knirirr wants a Webley-Fosbery automatic revolver. I picked this one to highlight first for two reasons.
The first is that when I looked it up I realized I didn't know anything about it. So let's look at Knirirr's dream gun and see what we are talking about.
Start with a Webley break top revolver. That gets you the basic revolver that George Fosbery modified. Now, set the top of the revolver to recoil, then cut a series of guide track in the cylinder so that the recoiling mechanism advances the cylinder and sets the trigger.
Now you have a 6 shot semi-auto revolver(!!). Commonly chambered in .455 Webley, which was a 265 gr. bullet running 650 to 750 fps, considered a powerful cartridge in it's day, it saw use in WWI. It was also considered as an option for the U.S. military and some test prototypes were made in .45 ACP.
Here's a clip from Forgotten Weapons detailing the operation of the Webley-Fosbery.
The other reason is much sadder. The country that developed and issued this weapon now essentially bans the ownership and use of the gun. As Knirirr mentions in his comment, there are strict laws about owning, reasons for owning, ammunition ownership, and use of what they call Heritage Firearms. His grail gun is not out of reach because it was especially rare, or even all that expensive. It is unavailable to him because there are laws, regulations, and because so many of the pistols were collected and destroyed. That lesson is one we in the United States would do well to be mindful of.