Depths for Granulated Rubber Bullet Traps: A Safety and Design Perspective

Ballistic Granulated Rubber Trap Depth Recommendations

Understanding the Recommended Depth for Granulated Rubber Berm Traps

In the arena of shooting range safety and design, one pivotal aspect to consider is the depth of granulated rubber berm traps. These traps serve a crucial role in capturing projectiles, ensuring that ranges are both safe for users and environmentally responsible. This article explores the recommended depths based on insights from Cumberland Rubber Supply, the U.S. Army, the National Rifle Association (NRA), and the Royal Canadian Mounted Police (RCMP).

Industry Standards and Research

• Cumberland Rubber Supply‘s study “Study on Ignition Risk for Granulated Rubber Media” delves into the performance of granulated rubber in bullet traps. While the depth isn’t directly prescribed, the study implies that deeper traps enhance safety by better capturing bullets and minimizing ignition risks.
• The U.S. Army publication “Bullet Trap Design and Ballistics Testing for Small Arms Ranges” (PDF) advocates for a minimum depth of 500 mm (approximately 20 inches) for granulated rubber media. This recommendation is based on extensive testing to ensure bullets are completely contained, preventing ricochets or back penetration.
• The NRA Range Design and Safety Handbook (PDF) posits that a depth of 900 mm (about 35 inches) is optimal for granulated rubber traps to safely manage various ammunition types. Nonetheless, they note that 12 inches (305 mm) might suffice for capturing most rounds, reflecting real-world application and testing.
• The Royal Canadian Mounted Police guide, “Range Design and Construction Guideline” (PDF), while not specifying an exact depth, emphasizes the importance of bullet containment in the overall design, which indirectly supports the need for adequate depth.

Consensus on Depth

The industry standard for the depth of granulated rubber berm traps seems to settle at 2 feet (610 mm). This depth has been widely adopted for several compelling reasons:

• Effective Bullet Capture: At this depth, granulated rubber can effectively stop and contain bullets of various calibers, reducing the chance of bullet escape or ricochet.
• Safety Against Ignition: The depth helps mitigate risks associated with bullet impact igniting the rubber media, which is a concern highlighted in several studies.
• Practicality and Cost-Effectiveness: Two feet is a balance between ensuring safety and managing the costs associated with deeper installations.

While some documents mention other depths like 19.7 inches (500 mm) or 35.4 inches (900 mm), the 2-foot (24-inch) depth is commonly seen as a practical standard in many shooting ranges. It’s not just about stopping the bullets but also about ensuring they are safely contained within the trap material.

High and Low Velocity Considerations: The depth of the granulate in line with the line of fire at the top of the trap for high velocity ammunition is between 35.4 and 39.4 inches (900mm and 1000mm). For low velocity weapons, the minimum depth should be 19.7 inches (500 mm) in the direction of the line of fire. For shooting in boxes in stop butts, the depth should also be 19.7 inches (500mm).

Design Considerations

When planning or revamping shooting ranges, several additional factors should be considered alongside depth:

• Ammunition Type: Different bullets might require adjustments in depth or composition of the trap media.
• Environmental Factors: Weather, ground stability, and local wildlife can influence the design and maintenance of berm traps.
• Regulatory Compliance: Local, state, or national regulations might impose specific requirements on range safety, including bullet trap design.
• Future Use: Consider potential changes in range activities or equipment, which might necessitate modifications to existing structures.

Consensus on Depth for Granulated Rubber Bullet Traps