Considering that no potato cannon uses cartridges, then I doubt that NFA applies to them? People make bowling ball mortars from gas cylinders and those have a

Considering that no potato cannon uses cartridges, then I doubt that NFA applies to them? People make bowling ball mortars from gas cylinders and those have a bore even larger than any potato cannon. Yet they are perfectly legal. Ofc here both are illegal, as the potato cannons cannot use combustion for power.