This video shows the different characteristics of a 5.56, a 9mm, and buckshot. While the 5.56 penetrates "slightly" more than the 9mm and the buckshot it does a lot more damage in the first few walls which means it will do a lot more damage to tissue. Note the 9mm did not expand. The shotgun did more damage and I did formerly use a 12 ga. for home defense there are a couple of things that matter a lot IMO.

First the noise of a 5.56 is not going to be as loud as a 12 ga. which means you might actually get to keep your hearing "if" you have enough sense to be wearing very effective hearing protection in your house. There are ear muffs that actually amplify all noise except gun shot noise. I keep them right beside my gun. You will wish you had something if you fire a gun indoors, believe me. The 9mm will not be as effective at stopping an intruder as a 5.56. Plus you most likely have more of a problem with ricochets with a 9mm due to the fact they don't fragment like a 5.56 round.

Also I believe drywall is a very poor medium to test over penetration. It is very soft and fragile compared to the bricks on the outside of your home and whatever might possibly be on the house next door. Tests need to be done with bricks or other material where results may be very different. I found another video where a brick wall was simulated. Both the 9mm and the 5.56 failed to penetrate the brick wall. The 12 ga. with buckshot destroyed the wall and clearly went beyond but the test didn't show how much beyond. Still that was the only test I've ever seen where they used a brick wall simulation. I include a link to that test. I will say I think the buckshot they used was extremely powerful. It has a 1600 fps speed while most buckshot is under 1300 fps.

In my particular situation I have a safe room and a zone where firing is going to be very safe compared to firing in a house very close to another house. My house is built back into a hill so that the back of the house is surrounded by dirt. And the structure behind the walls is not just a stud wall with drywall. It's 12 inch concrete blocks and behind that is a big wall of dirt. The only way a bullet would escape would be to ricochet (which slows it down) and then penetrate my front wall which has a stone exterior. And the nearest house in the line of sight is about 250 yards away. It just isn't likely for me.

A 5.56 has other advantages over a shotgun. It holds 30 rounds over the 6 my shotgun holds and even with the ammo in a sidesaddle holder that only gives me 11 rounds. That certainly would likely be enough. But there's also the recoil. My wife can fire the AR with no problems. She isn't likely to do nearly as well with a 12 ga. using buckshot.

There is a lot to be said for a shotgun. And I do have shotguns. I also keep a .45 near where I sleep because it's easier to get access to it. But it will be used to defend my movement toward my AR. I have a bright light mounted on the AR also which should blind any attacker. But you never know when a truly psychotic person might attack you whether from natural causes or drug induced. People can be very hard to stop when they aren't aware they are being hurt. I once shot a rabid fox 8 times in yhr head at point blank range with a .22 and it walked away. I was literally using the barrel of the gun to keep it away from me and I had the barrel about an inch from it's head. I shot it twice more with a 20 ga. shotgun and it didn't even flinch much less die. Finally a 12 ga. killed it. I want something I can be sure will disable a person in a mental state close to that of the rabid fox. A sensible person will withdraw at the first shot. A crazy person is liable to do anything and both me and my wife need to be able to keep shooting until the job is done.

Here's the video of the drywall test I mentioned before.


Here's the video of the brick wall test.