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How Do You Test Body Armor?Guns. Lots of guns.

By Christopher Beam
Posted Wednesday, May 23, 2007, at 6:50 PM ET
A pilot removes her bulletproof vest. Click image to expand.

NBC reported last week that military-issue body armor performs worse on ballistics tests than a commercial alternative called Dragon Skin. The Army responded by releasing its own report from last year, which went over the deficiencies of Dragon Skin. How do you test body armor?

Shoot it. Every type of body armor must pass a set of military ballistics tests before it's distributed to soldiers. The exact requirements for passing these tests—how strong the armor must be, and in what conditions—are classified, according to an Army spokesman. (Vests worn by law-enforcement officers must undergo a similar process, laid out in a document published by the National Institute of Justice.) But the Army's report on the Dragon Skin tests, summarized here, reveals that testers started by measuring, weighing, and photographing the armor vests, and then taking a series of X-rays. Then they subjected the armor to a series of gunshots, at different angles and from various weapons.

The shooting part of an armor test takes place in two phases. In the "penetration and backface signature" phase, testers set the vest against a clay tablet and fire six rounds at specified locations, including spots over the heart and on the sides. After each round, they examine the dented clay to measure how deeply the bullet impacted the armor. The test for lighter armor requires shooting at four vests—six bullets to the front of each, six to the back—which makes 48 bullets in all. If any of them penetrate the vest or dent the clay more than 44 millimeters, the armor will be deemed unsafe. (According to the Army's report on Dragon Skin, 13 of the 48 rounds shattered or ripped clear through the armor plates.) Military testers shoot more than just bullets; they also use "fragmentation simulators" to launch pieces of metal at a vest. The second phase of testing measures the armor's ballistic limit, also known as "V50"—the velocity at which a bullet will penetrate the armor 50 percent of the time. The tester shoots the vest 12 times, adjusting the bullet's velocity each time depending on whether the last one penetrated.

Testers also simulate different environmental conditions. For example, they might shoot the vest after spraying it with water. For the Dragon Skin tests, the Army looked at a temperature range of minus 20 to 120 degrees Fahrenheit, plus a high-heat 160-degree condition. They also gauged the armor's strength at high altitude, and after soaking it in oil or salt water.

Who conducts these tests, anyway? Many armor manufacturers send their new products to one of the two major ballistics testing facilities, H.P. White and United States Test Laboratory. These places have standardized shooting ranges and camera systems that document the tests. (See video of the Dragon Skin tests here.) Vests intended for police also have to be approved by the National Law Enforcement and Corrections Technology Center, which inspects for craftsmanship.

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Christopher Beam is a Slate political reporter.
Photograph of pilot wearing body armor by Stan HONDA/AFP.
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