The Single-Barrel, Break-Open Shotgun

[Talon]

When you talk of "moulds" and "balls" do you mean Musket/flintlock type ammunition? and it is perfectly legal to buy them UK.

Yes Tartar,just a simple lead ball like a musket fires.You can get slugs as well as round ball (think of a very large air rifle pellet)and the component parts are all perfectly fine to buy.

If you assemble a slug or ball cartridge though it immediately becomes section 1 ammunition and 5 years if you don't have the section 1 firearms licence with a slot for slug ammunition.

You don't even have to have a section 2 licence to own standard cartridges but you need one to buy them,go figure.It's another one of our strange firearm quirks.
So by all means buy a mould as it's perfectly legal to do so.Just stay legal and don't assemble the round.