As we mentioned in our last post, the powerful, accurate .223 has quickly become one of the most popular rifle cartridges in America–which also makes it a growing concern for anyone interested in bullet proof security. Unfortunately, the most common consumer-grade bullet proof windows simply cannot match the penetrating power of the .223.
A Brief Review on the .223
The .223 is the consumer version of the military’s 5.56 ammunition used in M16 assault rifles (which are in turn based on the Colt AR-15 semi-automatic rifle, and have become the model for modern sporting rifles). The projectile of the .223 has dimensions similar to that of the common .22 rifle cartridge (which are often used for teaching, target practice, “plinking,” and hunting very small game like squirrels, rabbits, and pest rodents). Both are shown in the image below (with the a .22LR on the left and the .223 on the right).
What you’ll immediately note is that although the bullets (that’s the top of the cartridge, the actual projectile) have similar dimensions, the .223 is clearly much more aerodynamic (and can be a bit heavier: .22s commonly range between two and three grams, while .223s can be as heavy as five grams).
The major differences is in the load: The much larger casing of the .223 allows for much more gunpowder to propel the bullet. Consequently, a .223 bullet travels up to three times faster than the .22 bullet–it’s one of the fastest bullets available to the public–and strikes nearly ten times harder.
The combination of a small, aerodynamic projectile moving incredibly fast makes the .223 especially hard to stop with standard bullet proof windows.
.223 Bullet Resistant Windows
Most bullet resistant windows currently installed in liquor stores and banks use monolithic acrylic. At around 1.25 inches, solid acrylic will easily stop several rounds from 9mm, .357, or .44 Magnum pistols. These rounds (shown in the picture below) are most often “semi wadcutters”: Snub-nosed projectiles designed to pancake, and thus efficiently transfer their momentum to their target for maximum stopping power at close range.
Acrylic bullet resistant glass takes advantage of this design: the bullet pancakes on the hard surface of the acrylic, and its momentum is gobbled up quickly as it smashes a handful of chips off the surface.
But the physics of a .223 is significantly different form that of a semi wadcutter; the .223 is slim, sharp, and moving fast–it’s designed to pop right through a barrier, even an acrylic bullet proof window.
Defending against the .223 calls for an entirely different approach. Not only must the ballistic glass be thicker–at least 1.625-inches thick, if not 1.75–it also needs to be of an entirely different composition. The only bullet resistant glass that’s going to stop a .223 is glass-clad polycarbonate. This laminated ballistic transparency is made by stacking layers of tempered glass and polycarbonate–a thermoplastic similar to acrylic, but softer and more pliable–interleaved with thin layers of epoxy.
When a .223 strikes a window made of glass-clad polycarbonate, the outer surface of tempered glass forces the projectile to partially pancake, spoiling its aerodynamic design. That tempered glass then shatters, and the inner layers of epoxy and polycarbonate flex like a backstop. Because this material is softer and denser than bullet resistant glass or acrylic, it often swallows the bullet up and holds it. While an acrylic-based bullet resistant window is unlikely to stop even a single .223, a rated Level 7 system using glass-clad polycarbonate ballistic glass will easily catch a burst of five or more of these bullets.
But a bullet resistant window isn’t just a hunk of glass-clad polycarbonate. In order to actually keep people safe, these windows need to be mounted in true ballistic framings, not 14 gauge steel–which the .223 round was designed to penetrate–or the fiberglass “packed” frames some bullet proof companies use to hold down costs. Bullet proofing experts like Total Security Solutions CEO Jim Richards always advise that their high-level bullet resistant windows be mounted in a specialized UL-rated bullet proof aluminum frame backed with internally integrated strips of ballistic fiberglass.
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FAQs
The only bullet resistant glass that's going to stop a . 223 is glass-clad polycarbonate. This laminated ballistic transparency is made by stacking layers of tempered glass and polycarbonate–a thermoplastic similar to acrylic, but softer and more pliable–interleaved with thin layers of epoxy.
How much polycarbonate does it take to stop a bullet? ›
Bullet resistant polycarbonate is one of the thinnest ballistic protection options available. Laminated polycarbonate systems can meet UL level 1 bullet resistance at just ¾”. This means that it is fairly light and easy to fabricate, cut, shape, notch, drill, and fasten into place.
Will laminated glass stop a bullet? ›
Manufacturers can engineer laminated glass to be bullet-resistant. Due to the composition of this glass and its layered construction, it won't shatter when a bullet hits it, nor will the glass fall out of its frame. Shatter resistance. Since the glass bonds to a layer of resin, it stays in place, even when broken.
What caliber does bulletproof glass stop? ›
Bullet Resistant Glass would withstand up to a . 50 Caliber round from a high-powered rifle. A . 50 Caliber round is most closely associated with military usage, and is not typically or commonly in widespread usage amongst most civilian products.
How many bullets does it take to break a bulletproof window? ›
Shoot 3–5 rounds of handgun ammunition at the glass.
So, keep shooting, since multiple bullets impacting in the same location may be enough to break through a thin sheet of bulletproof glass. If you're shooting a mid-power handgun like a 9 mm, you may need to fire 3-5 rounds to break through thin bulletproof glass.
Will polycarbonate stop a bullet? ›
Systems made of laminated polycarbonate can achieve UL Level 1 bullet resistance in as little as three-quarters of an inch. As a result, it is relatively lightweight and simple to construct, cut, shape, notch, drill, and fix into position.
Can 1 4 polycarbonate stop a bullet? ›
How Much Polycarbonate Does It Require To Stop A Bullet? The required thickness of the polycarbonate depends on the level of protection. For level 1 protection, 0.75 inches of thickness will work just fine. But if we go higher like level 2 and 3, the thickness will be required respectively 1 inch and 1.25 inches.
What are the disadvantages of laminated glass? ›
It is important to consider both the advantages and disadvantages of laminated glass before making a decision. While it offers enhanced safety, noise reduction, and UV protection, it also comes with a higher cost, increased weight, and reduced natural light.
What can I put in my windows to make them bulletproof? ›
Different Types of Bullet-Resistant Materials You Can Use for Windows
- Laminated security glass.
- Polycarbonate security glazing.
Legal Guidelines
In the United States, procuring and installing bulletproof glass systems is entirely legal, and there is no requirement for a police or government permit. However, the bulletproof glass must adhere to specific standards to ensure optimal protection.
So, while the UL 752 technically has 10 levels of bullet-resistance, only Levels 1 through 8 are commercially available. The strongest bulletproof glass used in typical commercial construction is UL 752 Level 8.
What's stronger than bullet proof glass? ›
Some materials and technologies that are stronger or offer enhanced protection compared to conventional bulletproof glass include: Transparent Ceramic Materials:Transparent ceramics like alumina (aluminum oxide) and sapphire are extremely hard and can offer improved resis.
What is the highest quality bullet proof glass? ›
At this highest of all security levels, only one bulletproof glass is secure enough. SILATEC. Compared to conventional armored glass, it is not only safer. It is also amazingly better in other ways – as you can see and read here.
Can bullet proof glass stop ar15? ›
Our glass is lightweight, but do not let this deceive you. It will resist gunfire from even the most common weapons used in mass shootings: the AR-15 and AK-47 rifles.
How expensive is a bulletproof window? ›
Bulletproof glass costs around $30 to $100 per Square foot. Factors like glass types, thickness, level of safety, and labor cost vary their cost. Expect to pay around $1200 to $20,000 for quality bulletproof glass.
Can a brick break a bullet proof window? ›
This also eliminates the threat of smash and grab attacks, because intruders simply can't break bulletproof glass, even if they repeatedly smash the pane of glass with a brick, crowbar, or another weapon.
How much polycarbonate do I need to stop 9mm? ›
The 9mm UL. 752 Level 1 protection is achieved by laminating a ½” acrylic sheet between two layers of 1/8” Polycarbonate.
Can a 1 inch plexiglass stop a bullet? ›
How thick does Plexiglass need to be to stop a bullet? Around 1.25”, depending on the caliber of the bullet. This thickness can stop bullets from 9mm, . 44 Magnum or .
How much force can polycarbonate take? ›
As a comparison, polycarbonate is about 30 times stronger than acrylic and about 250 times stronger than glass. Polycarbonate enclosures can withstand 900 pounds of impact. Because polycarbonate is so much stronger than these other materials, it is more resistant to breaking under pressure or impact.
How thick does Lexan have to be to stop a bullet? ›
Against some, it needs to be 10 cm or thicker. Against others, 2 cm will be enough.
