Study on ignition risk for granulated rubber media

Granulated Rubber Media

Rubber media is one of the best products on the market when it comes to increasing range safety. Rubber media berm traps are one of the most commonly used setups. Its popularity is increasing throughout the industry and is soon positioned to be the industry standard and possibly already is.

The product provides a broad range of benefits to improve the shooting range experience. Rubber media is suitable for both indoor and outdoor shooting ranges. The product has the ability to reduce airborne lead dust, prevent ricochet, improve acoustics by absorbing more sound and substantially increase range safety. Rubber media also reduces the barrier to entry costs by as much as %30.

Rubber media is used in thousands of ranges across the world. However, one fear regarding rubber media traps is the potential for smoke or fire risk. To dive into this concern, a study was conducted with architectural and range experts on the topic.

The question is, “what can increases fire risk when using a granulated rubber trap?” Can a high round temperature increase the auto-ignition rate for rubber media?

To start, we can look at the study of ignition by rifle bullets. Experiments were conducted to examine the potential for rifle bullets to ignite organic matter after impacting a hard surface.

This study suggests kinetic energy can convert into heat. However, this process should not occur when shooting into a rubber trap at recommended depts. A minimum of 2 ft deep rubber will decrease kinetic energy conversion. (minimum/measured perpendicular to the trap face) Range experts will often suggest exceeding 2 ft if possible.

Typical velocity and kinetic energy of common small arms cartridges (U.S. Army 1994). Note: 1lb = 7000 grains.
Conversion of energy from potential to thermal and kinetic energy during firearm discharge.

When you can decrease the potential for kinetic energy will only be left with the natural round heat. The round will continue to cool from leaving the gun barrel.

The next factor that can cause issues with round heat is a clean trap. This means the trap needs to be clear of contaminants. (As best as possible) This is the sole responsibility of the range operators.

Contaminants can range from poor quality granulated rubber media to low autoignition temperature materials in or around the trap.

These materials can include straw, sticks, grass, brush, paper, cardboard, gunpowder, plastics, liners, etc. if these contaminants have the potential for a low melting point, issues can occur.

The combination of improper depth, as well as contaminants, can provide grounds for potential issues. If the backstop is not at the proper depth and contaminants with a low auto combustion rate is present, the likelihood of an incident can increase.

Next, to note, the quality of the rubber can exhibit issues. Rubber media that is not properly filtered or comes from a poor source can be problematic. Low-quality rubber products that include bladders, tread, fiber, and metal still can be prone to issues.

High-quality fiber-free granulated rubber must be used to ensure a clean trap. Granulated rubber media offers super ballistic energy absorption no matter what angle the projectile enters the pile. Installers and designers must make sure the materials are as pure as possible.

When mixed with high bullet surface temperature and extenuating circumstances, the above factors can contribute to a potential incident. The majority of these examples can be eliminated with proper design and guidance.

Additionally, Range experts typically treat the rubber media with calcium carbonate or similar (intended fire retardant) products. This robs oxygen to inhibit potential issues. This is merely a safety net in the same vein as a seat belt to a bad driver.

Studies and tests reveal contaminants, and improper design can lead to the potential for smoke or fire risk. Efficient traps will decrease kinetic energy and provide an all-around safe granulated rubber trap. It is essential to design traps with the proper guidelines, free of contaminants, and use a high-quality rubber source. Lastly, use treatment to mix in with the rubber media for added safety.