Zonie, please at least let me clarify the situation before you cut me off -
Here in UK we can own MUZZLE-LOADING handguns of the usual BP ignition design - cap and ball.
We can also own any design in the traditional style, Remington, Colt, Remington, Spiller and Burr, Rogers & Spencer, Griswold & Gunnison et al, that have been modified with a NEW cylinder that is designed to shoot a minute charge of a modern propellant and, usually, a wadcutter bullet specifically designed for it. Many more shots can be obtained out of a pound of modern powder at 4.5gr at a time, rather than go through the hassle of getting BP, which needs licensing and dedicated storage. They utilise shotgun primers for ignition, and use a loading stand. They are STILL classed as a muzzle-loader, because they ARE muzzlel-loaders
As Jim notes, Alan Westlake, noted hand-gunner of the past and modern-day gunsmith, and Alpha Engineering, both make adaptations to MODERN revolvers using shotgun primers. They are, of course expensive - what else? and you either have to surrender your old cylinder for destruction and install the new one as a one-for-one entry on your Firearms Certificate [FAC], or have the new cylinder added to your FAC, as some do, so that if the mood strikes them, they can shoot the proper stuff.
We can, of course, own ANY kind of regular BP muzzle-loading handgun on MAINLAND UK - England, Scotland and Wales. Only in Northern Ireland, also part of the UK, can you legally own any cartridge-firing handgun that still looks like an ordinary item, although there are exceptions which are both costly and VERY constraining, that I'm not going into here.