Yes functional artillery, legally a destructive device which is a catch-all category and it depends on the ammunition, many people use training ammunition which doesn't have explosive because a artillery shell with a certain amount of explosive requires it's own tax stamp per round. Legally it's not a license but a document proving you paid the transfer tax following a background investigation. There are some odd rules for specific type of items. This is the sort of thing you should talk to a lawyer/ organization that specializes in the process. You can also get machinegun, silencer,short barrel rifles/shotguns legally through the same process.

https://youtube.com/playlist?list=PL9e3UCcU00TROa-o4xJsJ5UKS2b_PWKSB&si=BqWpSjD7hd59-MC8