Biden may actually be giving good advice to his audience. Double barrel shotguns are simpler than an AR-15. So simple that given enough time and an instruction video even anti-gun Democrats could probably fire off a shot or two.
His advice is entirely consistent with Security Theater advocated by most government types. He is suggesting people “Do Something” and they will feel better even if it accomplishes nothing that helps your situation.
Or instead of being onto something he could just be on something. Was he in Colorado testing out the local herbs when he shared his stupid thoughts with us?