To find out how an AR-15 penetrates interior walls, I built some---and then shot 'em up with a bunch of .223 Remington ammo.

To find out how an AR-15 penetrates interior walls, I built some—and then shot ’em up with a bunch of .223 Remington ammo.

Is an AR-15 appropriate for home defense? That’s a really big question, isn’t it? Way too big a question for a single article to address in adequate detail. So we’ll look at one issue at a time.

First, since AR-15 rifles cause all nature of mainstream media histrionics, we’ll consider the “high-power” issue, which in a practical sense, translates to penetration. If you torch off a .223 Remington or 5.56mm round indoors, will the building explode? Listening to the news, you might think so.

More rational, and less pants-wetting thoughtful consideration yields a different conclusion when we look at penetration specifically. If you shoot an AR-15 inside your home or apartment, and miss your target, will the projectile continue to pass through interior walls, exterior walls, cars, dump trucks, and eventually the nearest ocean before embedding itself deep under the sea floor?

These are curious questions. Being curious, I decided to build some very small walls and shoot them with an AR-15. I shall call them mini-walls.

I shall call them…mini-walls. I built four in total, each with drywall on both sides.

I shall call them…mini-walls. I built four in total, each with drywall on both sides.

When considering home defense options, from strictly a penetration point of view, the basic question is: what will over-penetrate through walls, furniture, and your shiny new Ninja Blender? A heavier and slower pistol round, or a very light and fast rifle round?

The thing about light and fast bullets is that they tend to get upset–specifically, fragment or tumble—when they hit harder things like walls or furniture. Tumbling and fragmenting both result in a very rapid loss of velocity and energy, therefore a lightweight rifle projectile going somewhere around 3,000 feet per second may actually have less unwanted penetration than a pistol round traveling in the 1,000 feet per second range.

Before sharing results, I should present a couple of disclaimers.

  • I suck at construction, so if you are a professional carpenter, just hold your lunch down while looking at the photos of my mini-wall construction efforts. I’m only shooting them to pieces, not putting them in my house.
  • I didn’t paint the walls. This may sound trivial, but several coats of dried paint are hard, and likely to make some difference in the rate that lightweight, high-velocity bullets break apart.
  • The walls are close together. As you’ll see, some of the projectiles started fragmenting pretty quickly. If they had more time to spread out before hitting the next wall, I suspect they would have lost a lot of energy. Think of a shotgun pattern. When the pellets are still “clumped” together at short-range, there’s more penetration than when they spread out to a three-foot pattern a little further out.
  • I’m not a ballistic scientist. I just got curious, decided to do some basic testing, and share what I found. Do with the findings what you will.

With all that said, I looked at two different “interior wall” simulations. In one scenario, I used drywall (Sheetrock) only. I assumed the projectiles only hit drywall material of multiple walls. For the other scenario, I added a piece of 3/8-inch particle board between walls one and two—just to simulate junk inside walls like cross beams, furniture, or any number of other things besides wallboard that may be inside a home. All shooting was done from “indoor” ranges of five yards.

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