Testing Bullet-Resistant Glass

Bulletproof Products

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Most bulletproof glass systems sold in the United States are tested to the rigorous “Standard of Safety for Bullet-Resisting Equipment” (aka “UL-752”) established by Underwriters Laboratory (the nation’s leading third-party product safety certification agency). Although there are several competing standards for bulletproof safety, most US builders favor the UL 752 specification, which is slightly more stringent when it comes to possibly dangerous debris ejected by the inside surface of a sheet of bullet-resistant glass. These chips, called “spall,” can injure people in the protected area, although all would agree that a little flying glass is preferable to getting hit by a shotgun slug.

TESTING BULLET-RESISTANT GLASS

Few companies actually have their materials tested by the Underwriters Laboratory.  Instead, they turn to a dedicated materials lab that scrupulously follows the UL standard.  In the case of UL 752, the material to be tested is securely mounted 15 feet from the muzzle of the test firearm (which is itself locked into a bench rest).  A clean piece of 1/8th-inch-thick corrugated cardboard (called a “witness plate”) is mounted 18 inches behind the test piece.  The witness plate is checked after each shot in order to indisputably establish not just whether or not the bullet beat the barrier (which tends to be pretty obvious), but also whether there was any spalling.

The eight levels of UL standards for bullet-resistance are broken into three groups, each with its own protocol:

LEVEL 1 THROUGH 3 BULLET-RESISTANT GLASS

For Level 1 through Level 3 bullet resistant glass (meant to protect against 9mm, .357 Magnum, and .44 Magnum rounds), a fresh sample must stop:
* Three shots within a 4-inch triangle with no spalling on the “protected” side
* Three shots within a 1.25 to 1.75-inch area (some spalling is acceptable)
* One unsupported edge shot (some spalling is acceptable here, too)

LEVEL 4 AND 5 BULLET-RESISTANT GLASS

Level 4 or 5 bullet-resistant glass is meant to stop a single shot from a .30-06 or AK-47 assault rifle, respectively.  Samples must stop:
* One center shot
* One unsupported edge shot (some spalling is OK)

LEVEL 6 THROUGH 8 BULLET-RESISTANT GLASS

These levels of security are intended to stop bursts from submachine guns and assault rifles, such as UZIs, M16s, and AK-47s.  Level 6 through 8 bullet-resistant glass must stop:
* Five shots within a 4.5-inch square
You might assume that a bullet-resistant system made from materials tested to UL standards is as bullet-resistant as its component pieces. Nonetheless, any assembly sold as having been verified against UL standards must be independently tested under laboratory conditions and meet the UL specification.

Eight Levels bullet resistance

BUILDING WITH BULLET-RESISTANT GLASS

Total Security Solutions has all of its systems, components, and assemblies independently tested by H.P. White Laboratory.  In contrast to UL, which tests everything from bike locks to Easy-Bake Ovens, H.P. white is the global leader in testing building materials for security and architectural uses and developed many of the industry’s first ballistic glass testing protocols.  As Total Security Solutions vice president Jim Richards explains, “These are the people we’ve used for years.  They’re reliable, timely, and you get accurate feedback and information, which is really important:  I want to know how well it passed, or exactly how it failed.”

Jim shared one of the detailed reports produced by H.P. White after they tested a new door that Total Security Solutions has developed to UL Level 4 standards.  The White report confirms that the test door was mounted dead vertically (even a slight angle can decrease the bullet’s velocity upon impact) 15 feet from the muzzle of a .30-06 rifle.  The report goes on to confirm the witness plate placement and material (1/8th-inch corrugated cardboard mounted parallel to and 18 inches behind the test sample), as well as the room’s temperature (an energy-conscious 69 degrees), relative humidity (50%), and barometric pressure.  The report likewise lists the names of the gunner and recorder, as well as which specific lab firearm was used in the test.  Total Security Solutions’ new door was then shot eight times: once in the center of its bullet-resistant glass window, once at the door seam, once on the door’s face, once on the ballistic window’s seam, once along the thin gap where the door meets its frame on the hinge side, once where the door meets the frame on the knob side, once in the lock, and once in the hinge itself.  Additionally, H.P. White measured and confirmed each bullet’s velocity twice along its path between muzzle and door, so there can be no doubt that each shot struck at full force.

In case you’re wondering, the door passed with flying colors: Eight shots with no penetration and no spalling.

 

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