Water Balloons vs. Bullet

Here’s Sumdood from National Geographic, asking that question: How many water balloons does it take to stop a bullet — a .44 Magnum from a Smith Model 629, to be specific?

If you’re enough of a gun nut to read this site regularly, you’ll be pretty close to the answer, having seen other instances of firing into water. (In fact, it’s how bullets are recovered in crime labs, for forensic ballistics). But you’ll seldom see it given so much of a reality-TV build-up, with the payoff coming in slow-motion video.

The key bit is the slo-mo at the end, where they’re showing the bullet speed in fps as it declerates through each balloon. After the second balloon, the mighty .44 Mag is down to airsoft levels of fps, and it only goes downhill from there.

So why don’t they use water balloons as armor? Well, the first shot lets all the water out, and nobody fires one shot at you these days. Plus, it’s about as heavy as armor gets.

5 thoughts on “Water Balloons vs. Bullet

  1. Ernie

    Water [frozen] as armor:

    Pykrete is a frozen composite material made of approximately 14 percent sawdust or some other form of wood pulp (such as paper) and 86 percent ice by weight (6 to 1 by weight). Its use was proposed during World War II by Geoffrey Pyke to the British Royal Navy as a candidate material for making a huge, unsinkable aircraft carrier. Pykrete has some interesting properties, notably its relatively slow melting rate (because of low thermal conductivity), and its vastly improved strength and toughness over ice; it is closer in form to concrete.

    When we fired a rifle bullet into an upright block of pure ice two feet square and one foot thick, the block shattered; in pykrete the bullet made a little crater and was embedded without doing any damage.


    1. Hognose Post author

      The Habakkuk project reminds me of Tom Swift and his Ocean Airport, a book that was probably my late uncle’s property when he was a boy, that I found in my grandparents’ summer house and read when I was a boy. The two generations of Tom Swift books produced two generations of happy STEM students. The science and engineering in the books was godawful (and the writing, too), but the idea of a science/engineer hero was very empowering to boys who all ache to build stuff.

      1. Ernie

        It occurs to me that I have a large collection of otherwise useless newspaper and a source of water.
        And it isn’t getting over 20 degrees for the next 7 days at least.
        I should shoot some Pykrete, cause SCIENCE!

  2. neutrino_cannon

    Water is actually better protection, pound for pound, than steel against shaped charges. A simple hydrodynamic approximation of shaped charge penetration has the total penetration as a square root function of the ratio of the density of the liner material and the density of the armor.

    Why don’t tanks use water as armor? They could, and it would be reasonably effective, but since tanks are going to be filled with fuel anyway, and fuel works about as well as water, they do that instead.

    Getting the fuel cells to pull double duty as anti-shaped-charge armor is just one of the tricks for getting tanks to survive modern weapons.

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