Are potato cannons legal in the UK?

Answer 1

Pneumatic potato cannons under 3 ft pound are legal, but anything more powerful is considered a firearm, and should technically require a lisence, in reality though this is virtually impossible to enforce, as most are home made. So really as long as your sensible, only use it on private property (preferably in a rural area), and dont use it for any evil deeds, you wont get into any trouble.

Combustion ones that use a flammable aerosol (usually hairspray), are a bit more of a grey area. They probably are considered a firearm, but i found nothing that says you can or cant make them, so again, just be sensible.