Imagine you're playing tower defense.

Now picture an American military base. They're pretty big, right?

Now imagine how many of these shotgun towers you need to secure the paremeter based on the firing range of these weapons, then imagine how many you shotgun towers you need to defend the interior of the base from drones that don't attack from the side but instead come in from the middle because they can fly.

How much ammunition can each of these shotgun towers hold? What happens when it runs out? Does a human have to go over there and refill it? What kind of equipment do they use to do that? How much time does this take and how much fuel does it consume? What is the opportunity cost of this?

Now that's just one military installation. How many does the US have? Are you going to put these shotgun towers outside the homes of high ranking military officers? The roads that they take to go to work?

What's stopping someone from doing this kind of drone attack on the highway to the military installation timed with the morning or evening commute? What's the counter to that?

Automated shotguns are not an economically viable defense to the threats that I described in my previous post.