Bulletproof steel doors are an attractive option for improving security by placing a ballistic-resistant barrier between a perceived ‘safe side’ and an area where there is a live threat. They are practical, heavy-duty solutions that can seal a safe room or entryway to significantly delay the time it takes for armed individuals to force entry. Steel doors can also stop multiple rounds of varying velocities depending on their Underwriter’s Laboratory classification. So, just how ‘bulletproof’ are bulletproof steel doors?
Steel Armour: A Centuries-Old Solution
To fully assess the protectiveness of bulletproof steel doors, it is worth looking back at why this particular alloy has proven so effective in armor plating throughout history. Historians believe that it was first used in Europe to engineer interlocking chainmail shirts to protect foot soldiers and cavalry from injury by stabbing and projectile weapons. As the weaponry of the era became more sophisticated and deadly, chainmail was gradually supplanted by armor plates which culminated in the medieval age’s iconic suit of armor.
A similar shift in armor design occurred in 16th Century Japan, although the samurai had already been using their characteristic plate armor for hundreds of years at this time. Steel was introduced into these plates as a direct response to the introduction of European firearms. The outstanding hardness and shock resistance of steel made it perfect for personnel protection by shattering comparatively soft projectiles. It has been used in various formats as a bulletproofing solution ever since.
Advantages and Drawbacks of Steel Plates
Steel is so effective at stopping bullets because the alloy can be tailored for the ideal mix of hardness and toughness, which means it can resist deformation and cracking when impacted by an incoming projectile. These material properties are determined by the grade specification and plate chemistry. However, the thickness of the plate is also important, as the destructive potential of a bullet is determined by several factors, primarily velocity. Essentially: the thicker the plate, the greater the measure of protection.
Increasing plate thickness to improve its ballistics-resistant credentials only works up to a certain point, before running into commercial and practicality issues. Steel is not cheap, and any increase in thickness will also increase both the weight and the mass. In the context of bulletproof steel doors, this would present unsurmountable challenges for both architects and daily users.
Bulletproof Steel Doors: Effective, Practical Solutions
Fortunately, bulletproof steel doors do not utilize the extremely thick plates typically associated with armor applications. The solution is built on centuries of development in ballistics management via layered materials – a composite solution reminiscent of the original armor used by samurai pre-16th Century.
A skin of cold-rolled steel is fitted on a hollow door built of ballistic-grade fiberglass that is filled with high-performance foam insulation. This composite layering system provides the ideal compromise between everyday practicality and ballistics resistance. It also provides the answer to the question: how bulletproof are bulletproof steel doors?
Armortex can engineer bulletproof steel doors to satisfy all eight levels of the Underwriter’s Laboratory (UL) classification. Entry-level bulletproof steel doors will resist multiple shots from a .44 magnum at relatively close range, while range-topping products with level eight protection will withstand several shots from high-powered rifles. You can read more about the levels of protection outlined by the UL in our previous blog post Bullet Resistant Glass: Explaining the UL Rating System. Contact a member of the Armortex team of you have any questions.