That Ain’t Bulletproof Glass

If you’re looking for examples of what happens when bulletproof glass gets shot, a quick Google or YouTube search is likely to leave you more confused than when you started.

The first thing you need to know is that, in modern installations, the vast bulk of “bulletproof glass” is actually “bullet resistant plastic”–usually sheets of acrylic more-than one inch thick, or laminated stacks of polycarbonate, or combinations of the two. Lots of the “bulletproof glass” you’ll see getting shot online is tempered glass–basically no different from your living room windows or a car’s passenger windows (albeit thicker). While tempered glass has its place in the history of bullet-proof living, it hasn’t been on the cutting edge since Truman was in the Oval Office.


Here’s one example. At first brush, this seems like impressive security: 2.5 inches of “bulletproof glass” should offer Level 8 protection and stop any pistol fire, as well as shots from a deer rifle, a 12-gauge shotgun, or bursts from an M16 or AK-47. But in this video, they demolish this bulletproof window with a .50-cal rifle and a couple standard hunting rifles.

We really shouldn’t be shocked that this “bulletproof glass” doesn’t hold up. For starters, .50 caliber rifles are relatively uncommon, remarkably high-powered guns. Mostly used in the military as sniper rifles, no consumer-grade bullet-resistant system will stop a .50-cal rifle bullet, which requires Level 10 bulletproof glass (usually three or more inches of polycarbonate plastic, which equates to almost half a foot of tempered glass).

Even granting that the .50-cal was never going to stop for 2.5 inches of tempered glass, this system still should be able to stop the rifle shots, shouldn’t it? Even after its been compromised by the .50 cal bullet? Certainly it should: Some commercial bulletproof systems provide Level 8 security with just under 2.5 inches of laminated glass. The key term here is laminated; the reason that the window pane in this video doesn’t stop those .30-cal bullets is because the glass isn’t properly laminated.


For comparison, check out this video of a piece of properly tested, laminated bullet-resistant tempered glass being shot by the weapon for which it is rated:

Not only are the bullets stopped, but there is also no spalling–no chips or flecks of glass pop off the back, where they might injure one of the people the bulletproof glass is designed to protect. That’s because these sheets of 3/8-inch tempered glass are interspersed with super-thin layers of polyurethane. During the manufacturing process these layers are stacked like a Dagwood sandwich, then pressed together and baked. The resulting piece of glass, although composed of layers, functions as a single sheet. When a bullet strikes the first surface, it breaks the glass, but the rubbery urethane holds the pieces in places, and acts like a trampoline, flexing without tearing. This eats up the bullet’s energy.

In the first video, it’s pretty clear that the “bulletproof glass” is just a stack of unlaminated glass. The bullet hits the first sheet, shatters it, and the shards fly out, making way for the bullet to keep driving forward. It’s little wonder that these shooters popped through the barrier with a hunting rifle. With two or three shots, they probably could have broken it with a pistol, even though just an inch or so of properly laminated glass can stop such a 9mm in its tracks.


No word on either the type of ballistic glass nor the caliber of the rifle in this vintage clip, but we can all agree that’s one confident lady:

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