Three researchers recently patented a new type of bullet capable of self-destructing after traveling over a predetermined distance. Brian Kim, Mark Minisi, and Stephen McFarlane filed collectively for the patent. The concept could, theoretically, be used in various calibers of small arms munitions.

"We wanted to protect the U.S. government's interests and position," McFarlane said about filing the patent.

Designing the Unstable

The idea behind the new and advanced projectile is that it might help limit accidental injury (or even death) during battle or in other operational settings and environments. 

"The biggest advantage is reduced risk of collateral damage," McFarlane said. "In today's urban environments others could become significantly hurt or killed, especially by a round the size of a .50 caliber, if it goes too far."

US Army

So how does the bullet know when to self destruct?

The U.S. Army explains that when one of these limited-range projectiles is fired, a pyrotechnical material is ignited at the same time and reacts with a special coating on the bullet. The pyrotechnic material ignites the reactive material, and if the projectile reaches a maximum desired range prior to impact with a target, the ignited reactive material transforms the projectile into an aerodynamically unstable object incapable of continued flight.

In one concept, the projectile is rendered unstable by the melting of a copper jacket, which produces a highly irregular shape. In another, the projectile is rendered unstable by the separation of the cylindrical portion from the base portion and the separation of the penetrator from the projectile assembly.

The researchers add that the desired range of its limited-range projectile can be adjusted by switching up the reactive materials used. 

"Conceptual designs were ran through and evaluated via modeling and simulation," Kim said. "Three concepts were submitted with the patent, however, not all were feasible," he said.

"A proof of concept test was perfected and results indicated the need for concept refinement and pyrotechnic mix improvement," Kim said.

Army Accomplishment

Currently, the invention is nothing more than a proof of concept, and funding for the project has ceased, but the Army researchers involved are confident that they're onto something transformative. The three researchers believe the idea will resurface.

It may be a while before this idea becomes a working prototype, let alone an actual tool used in the field. Despite this, and the lack of funding, McFarlane said, "This was the first patent we applied for that has been approved. That in itself is an accomplishment."

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