As far as I know, it’s perfectly legal to own a bazooka. It’s basically no different than a length of sewer pipe without the rounds. The rounds, though, unless perhaps if they’re non-explosive dummy rounds, are destructive devices and you’d have to pay the NFA tax on EACH ONE.
It’s also legal to own a tank. There are a good number of collectors out there. Rounds for the gun would require the NFA tax stamp for each one.
Well said and you can also own a civil war cannon, and shoot it when you please.