Why Airport Metal Detectors Won’t Pick Up Bullets

Yesterday, we wrote about how they found a single bullet found on the floor of an Alaskan Airline. We noted, “You
d think that
d be something the metal detector would pick up.”

Michael wrote in to say, no, you could wear a full lingerie set made from .22 caliber bullets, but…

    “Metal detectors won’t pick it up. They work by inducing a magnetic field in ferrous metals, and then sensing the resulting field.

    Cartridges (bullets) are composed of: copper, lead, brass, smokeless gunpowder (nitrocellulose/nitroglycerin), and a primer which does have some ferrous metal in it, but its so minimal I seriously doubt anything would pick it up. The primers [weighs] only a few grams, and only about 1/2 of its mass is metal.

    …That and something like a 747 is designed to fly (and remain pressurized) with something like 5 or 6 windows completely removed… A single (hell, an entire magazine) shot won’t cause the aircraft to depressurize.”

Thanks, Michael, that is some good chunky info. However, our concern wasn’t about someone shooting the windows and depressurizing the airplane. Rather, we were concerned about the bullets being used to depressurize people’s skulls, as in the Pro Diablo Ultimate Hunting Slingshot?

UPDATE: Nick writes,

    “That email about metal detectors only detecting ferrous materials is a load of bunkum – metal detectors work by inducing a current in any conductive metal (eg, any metal) – it doesn’t have to be ferrous to be detected. See [here at howstuffworks for] details.

    The real reason it wouldn’t detect a bullet is that even in most paranoid airports, the threshold is set too high for a single bullet to set it off. If your [measly] wristwatch with a metal band doesn’t do it, nor will one measly bullet.”


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  1. Gari N. Corp says:

    So that business in In The Line Of Fire, with Malkovich, and the rabbit’s foot, and the bullets, and the plastic gun, and the metal detector, that was all bollocks, was it? Crushed, I am.

    And that whole tubby Auric Goldfinger flying out of the depressurised plane. bollocks as well, right?

    Any other classic thrillers you want to sprinkle with your cynic-dust, you heartless brute?

  2. Um… your common or garden metal detector does indeed work by inducing a magnetic field in metal. Any metal. Anything conductive, actually; a big chunk of graphite in your pocket would probably set one off. It has to do with Lenz’s Law.

    If metal detectors only detected ferrous metals, those dudes on the beach trying to find coins with a Radio Shack product would pretty much never find anything of value. Would you buy a “treasure hunting” product that could only detect iron and nickel?

    Oh, and you could carry a nice bronze knife onto any plane you liked :-).

  3. AcidReign says:

    …..Unless you’re a religious jyhadist, an airplane is about the stupidest place in the world to commit a violent crime, anyway. You’ve got to know where you’re going to run to when it’s over, and in the air, you’re pretty much screwed, especially if the passengers aren’t sucked out of the window!

    …..When I was a kid, my brother and I found a box of .22 LR bullets in a neighbor’s trash. Since we had no gun, we shot them out of a wrist-rocket slingshot. Imagine our surprise when we shot one at a cliff face at Desoto State Park, and hot lead came whizzing back right at us! Fortunately, .22s don’t have lethal velocity after a couple hundred yards! (They do sting, though!) And the park rangers went nuts, searching everyone for guns…

  4. Paul D says:

    Didn’t Mythbusters do a show about explosive decompression?

    They took an old passenger jet, sealed it up, pressurized it, then remote controlled a gunshot to one of the windows.

    Nothing happened.

    Still, it is ideologically upsetting that metal detectors don’t detect bullets.

  5. Kishi says:

    Oh, and you could carry a nice bronze knife onto any plane you liked :-).

    Great, now the next time I fly, I have to worry about terrorists from 2000 BC!

  6. GenXCub says:

    Hey Paul… at least we all have the same TV habits… I said that in yesterday’s bullet story: