In my opinion, most ordinary civilians would be best served with a large-caliber (https://clayeolsen.com/archives/222) double-action revolver or a shotgun as a home defense weapon. I talked about some previous home shotgun suggestions here: https://clayeolsen.com/archives/359. I want to discuss some more considerations for shotguns here.
First, many ordinary civilians may want to purchase short tactical shotguns. These can be short-barreled shotguns (SBS), which require a tax stamp from the ATF, or perhaps have a pistol grip or a short stock. I recommend against this type of purchase because even though home defense ranges are short, you must still be accurate. These short shotguns make that much more difficult in stressful situations.
Second, some ordinary civilians may want to use a regular shotgun made for birds. These may have a 28″ barrel or longer. Depending on how you use them, these can work well. In general, though, I recommend purchasing a shotgun dedicated to home defense with a shorter barrel and a bright front sight (made for shooting things other than flying birds).
Third, some ordinary civilians may want to purchase a .410 shotgun. Here, ammunition selection is critical. Many handguns have been introduced that can shoot .410 shells along with regular .45 Colt or .45 Automatic ammunition. These handguns have rifled barrels, and the .410 defensive loads are made to shoot in rifled barrels (in most cases, this ammunition is labeled for handguns, but make sure with the manufacturer). Regular .410 shotguns have smoothbore barrels, and these rounds may not perform as well in those shotguns.
Given these considerations, what would I recommend? In general, I would recommend a 12 Gauge or 20 Gauge shotgun with about a 20″ smoothbore barrel and rifle-style (or ghost ring sights).
Here are some key questions:
How strong are you?
A fully loaded shotgun can be heavy. If you have a defensive room like the one I describe in my book, you can rest the shotgun on your defensive setup. Depending on what you are resting it on, you’ll need to lift it up to properly feed a pump-action shotgun with a bottom eject (common for left-handers).
What are the risks of overpenetration?
Any firearm used in the home risks overpenetration. Ken Whitmore has done a nice job of testing various firearms and loads here: https://www.pewpewtactical.com/home-defense-overpenetration/. A key point is that regular drywall is not a very good stopper. In my book Beyond Weapons, I discuss ways to help in this regard.
Do you have a lot of property to protect?
In my book, I discuss why it is usually a bad idea to confront 2-legged animals on your property. In this case, I’m talking about 4-legged animals that may be trying to get at your domesticated animals. Your home defense loads may not be right for this type of work.
Many pump shotguns are at a distinct disadvantage here. Unloading and reloading a pump shotgun with different ammunition is much more troublesome, and this process is also more likely to result in a negligent discharge. A couple of exceptions exist: (1) Mossberg makes the 590M, a magazine-fed shotgun. With the 590M, you can have two magazines, each with different ammunition – one for inside the home and one for the property. Some high-visibility tape is all that is required to differentiate between them. (2) Some shotguns, such as Kel-Tec, have dual magazine tubes where each magazine tube can hold different ammunition. A selector switch determines which magazine tube is used. Extreme care must be used in a home defense situation as you don’t want to select the wrong tube and have massive overpenetration problems due to the wrong ammunition being used.
Also, you’ll want a very good light on any shotgun used outside.
How much recoil can I handle?
Unless you handload your own shotgun shells, you’ll be limited to factory ammunition. Low recoil ammunition is typically in 00 Buckshot or slugs, which may result in overpenetration. Ultimately, be prepared to test whatever load you choose (refer to Ken Whitmore’s test process in the link above).