Okay, now that’s a rabbit hole if I’ve ever seen one. Because: tanks are operated by a crew, not just one person.

So who on the tank crew needs this certification? Presumably, at least, the gunner—i.e. the person actually pressing the button to fire the cannon—would. But how about the owner of the tank? How about the driver, if that's a different person? Can the driver/owner of a privately-owned-and-operated tank just be a regular dude, and call in an expert (maybe someone from the National Guard) to sit in the tank alongside them as its gunner?

I know that ATF explosives experts are usually called in by e.g. YouTube science content-creators, to handle the actual "explosives" parts of explosives demos. But in such cases, the ATF fellow doesn't just set off the explosives; they also set them up, in fact usually sourcing the explosives themselves rather than trusting explosive materiel given to them.

In the case of a tank, the tank is already there on-site when the expert arrives; and its cannon shells are probably also already there on-site, as finished explosives. Would a destructive-devices-licensed expert insist on calling in an engineer for an audit of the tank's soundness as weapons platform, to ensure e.g. the cannon barrel will still be able to take the strain of firing after sitting unmaintained for decades? (And would that person need to be specifically trained and certified in Weapons Engineering to be able to sign off on the tank's soundness?) Would they insist on sourcing their own shells, or, if that's impossible (vintage/foreign tank where shells of the required shape can't be locally sourced), perhaps having them refurbished (opened, cleaned, re-filled with a known explosive mix, re-packed) by a trusted factory?

And do the rules change if the driver tells the gunner when to fire? In fact, would the answer to the licensing question be different depending on the type of crewed weapons platform we're talking about? Would you, as a vehicle owner, need a destructive-devices license to e.g. captain a gunboat in a private pond, given that it is usually understood that the captain of a ship has overriding authority for any decisions anyone else who has boarded their ship makes while on board (and so, in other words, can tell a gunner to fire off a missile whether the gunner thinks that's a good idea or not)?