Overheating gun barrels pose risks for Soldiers

Heavy, constant fire from a machine gun can cause temperatures inside the barrel to reach very high levels, raising the risk that the primer or propellant in the cartridge could unexpectedly ignite or “cook off.” That event could cause a weapons stoppage or injure a Soldier while attempting to clear a stoppage by removing a live round from the hot barrel. Frank Dindl, a mechanical engineer and prolific inventor at the U.S. Army Combat Capabilities Development Command Armaments Center at Picatinny Arsenal, New Jersey, has received a patent for a “coolant cartridge” designed to minimize the possibility of dangerous cook offs.
(Photo Credit: Patrick Albright)

PICATINNY ARSENAL, N.J. -- For some time, Frank Dindl has had “cook off” on his mind, but his focus has nothing to do with any barbecue competition.

Rather, Dindl is concerned with minimizing a hazard that has been a problem since machine guns were first invented. As a steady, heavy volume of rounds is fired over a short period, the heat inside the gun barrel climbs to very high temperatures.

If a round or cartridge inside the barrel heats up to the point that it reaches the ignition temperature of the primer or propellant, the cartridge could unexpectedly “cook off” or ignite. That might cause a weapon stoppage, which could be disastrous during intense combat. Moreover, the gunner could be injured if a stoppage leaves a live round in a hot chamber and the round goes off while the gunner is trying to clear the stoppage.

 “Current machine guns typically use easily removable, quick-change barrels so that the gunner or gun crew can swap a cold barrel for the hot barrel every couple hundred rounds,” said Dindl, a mechanical engineer at the U.S. Army Combat Capabilities Development Command Armaments Center, located at Picatinny Arsenal, New Jersey.

“This is fine in training, but not ideal in combat,” he added. “Plus, the spare barrel is a lot of extra weight for the Soldier to carry around. The technical challenge is how to keep the bore surface below the 400 degrees or so that produces cook offs.”

For decades, there has been a search for ways to eliminate the hazardous cook offs, thus reducing the need to change barrels and prolonging barrel life.

Dindl’s solution, for which he has obtained a patent, is a liquid- or powder-filled cartridge to cool and lubricate the bore of gun barrels. A primer is used to rupture the nose of the cartridge and propel the cooling material into the bore. The coolant absorbs heat from the bore of the barrel and is ejected from the muzzle of the weapon.

According to the patent, “the liquid or powder may include lubricants, preservatives, antifreeze, coolants, cleaners, or mixtures thereof, or other materials to enhance barrel performance. The liquid- or powder-filled cartridge is particularly well suited to externally powered weapons. Ammunition may be fed into the weapon using a mix of conventional cartridges and coolant- filled cartridges.”

The invention applies to cartridge cases made of brass, steel, aluminum, polymer, and other case materials. Each coolant cartridge contains enough coolant to offset the barrel heat caused by firing of about eight conventional cartridges.

Although he already has a patent to address cook off, Dindl continues to search for solutions. “I recently came up with another invention for cooling barrels that I like better than the coolant cartridge,” he said. “The patent application for this new invention should be filed sometime in the next nine months, and should issue in two or three years.”


Dindl has 25 patents to his name, some obtained on his own, and others with collaborators. The unceasing impetus to find new ways of doing things has been a recurring pattern during Dindl’s career. He first started working at Picatinny Arsenal in 1985.

“Then I left in 2004 to start my own business inventing things,” Dindl said. “I wanted to go out and invent things on my own. I did that for 11 years. Then I came back in 2015.”

Based on his output over the years, Dindl doesn’t view himself simply as someone with an engineering degree.

“I would say that I'm a terrible mechanical engineer but I'm a pretty good inventor,” he said.

“My philosophy is that I come up with crazy ideas, and then there are other smart people who can help me figure out how to make them work,” he continued. “One of the guys that I co-invent with many of my patents is Ken Jones. That's the relationship that we had. He's a contractor, but I've worked with him for 20 years.”

For Dindl, other colleagues at the Armaments Center are also a valuable resource. “If I need help with doing some kind of modeling or simulation, or higher level math, there are people who I can turn to. Sometimes I'll invent stuff that's outside of my area of expertise. I'm not very good at anything electrical, so obviously I turn to folks who are. They can tell me if my ideas are workable or not.”

Dindl said the Armaments Center is also fertile ground for problem-solving because employees get to learn about the needs of Soldiers, thus helping to shape his focus on finding potential solutions.

“Picatinny also gives us the tools that we need to be great inventors, to be able to come up with solutions,” Dindl said. “That's a part of the reason why I've been able to collect a fair number of patents. It's because I've been exposed to all these different things.” Dindl also noted the value of classes he took taught by Andrei Cernasov, the former associate director for innovation at the Armaments Center.

Lighter cartridge case operates at higher pressures
Frank Dindl is a mechanical engineer and a prolific inventor with the United States Army. Among his 25 patents is a polymer-cased 5.7mm cartridge that is 60 percent lighter than its conventional brass equivalent and can operate at higher pressures. For a year, Dindl carried in his pocket the inert models of both types of cartridges to show to people when he was seeking funding to develop the technology. Dindl works at the Combat Capabilities Development Command Armaments Center at Picatinny Arsenal, New Jersey. (Photo Credit: JESSE GLASS) VIEW ORIGINAL


Dindl said he doesn’t really have a standard approach to pursuing inventions, but has assimilated various nuggets of information and ideas over the years. One source of information includes the “TED Talks,” which are videos created from presentations at TED (technology, entertainment, design) conferences.

“One of the talks made a great point,” Dindl recalls. “It was to leave time to invent, to leave space in your schedule for not doing anything, so that you would have time to reflect on problems and to be able to think. Often, we're so busy managing projects that we don't take the time to give our brain the opportunity to reflect on problems.”

Invention ideas can also start to simmer in unlikely circumstance. “Some of my most productive inventions were in situations where I was forced to sit still, and I was in an environment that was very boring, like some of these conferences we would go to. People would be giving a presentation on a topic I wasn't interested in,” Dindl said. “I was stuck in a room, so my mind would wander. That's when I would often come up with ideas for new inventions, out of sheer boredom. You think about things that are interesting, and to me inventing stuff is interesting.”

At other times, an invention idea is birthed when certain strands of previously disjointed knowledge and experience seemingly bubble up at the right time, then coalesce into a solution. That may describe the process involving a patent that Dindl obtained in September 2020 for a lightweight cartridge case and weapon system that he calls his favorite patent.

“It enables the use of an all-polymer cased cartridge that is 60 percent lighter than conventional brass cased cartridges, is capable of operating at higher pressures than conventional brass cartridges, and produces about 25 percent more muzzle energy for a given cartridge size.

“With that one, I woke up at 5:30 in the morning on November 4th, 2015, with the idea that if I combine these three things that I've learned over my career. Then that will allow me to use an all-polymer cartridge case and cut the weight of the ammunition in half.

“I got all excited when I got to work that morning. I kept running calculations on the back of the envelope just to prove to myself that yeah, it could work. I was thinking about it before I went to bed, and got up the course of the night­­--my brain sorted out the problem--and the solution came to me. It was three things that I had learned that came together for that particular invention.”

On other occasions, invention ideas have a more roundabout timeline. Research and development that was done earlier for one project may yield a solution many years later for a different problem, Dindl said.

“I would say a lot of it is practice, too. The more you do it, the more you work on inventing things, the more you are able to train your brain to think like that.

“There are times when things pop in and out of your past life that trigger a response from you. They get your attention, consciously and subconsciously. At least in my case, it's not always a conscious decision. It’s not like I'm sitting down and saying, ‘Oh I'm going to come up with a solution for this problem.’ A lot of times I'm just aware of the problem. Inventing is not something that you can do to a schedule--at least I can't. Sometimes the solution comes to me very quickly, and other times it might be 10 years later.”


The process of turning an idea into a final product might be compared to a screenwriter in Hollywood who fervently believes he has a great idea for a movie. But just having an idea isn’t enough. Other people have to be persuaded that the idea is worth the time and investment to further refine and develop.

The process may take an indefinite, unpredictable course. Prospects rise and fall along an irregular path, influenced by any number of unforeseen events.

For an engineer like Dindl at the Armaments Center, the process begins with paperwork--the invention disclosure. “It describes the patent so that the patent attorney can understand what your invention is, and it starts the process so that you then can brief the invention evaluation committee,” Dindl said. “They are the ones that decide whether or not Picatinny is going to spend the resources to prepare and file for a patent application for you.” There is no cost to the employee.

Dindl said he is available to help young inventors to prepare a patent disclosure, in large part to help them avoid his own early experience. “I didn’t know how to fill out the paperwork, and I was intimidated by it,” he remembers. “I ended up spending an incredible amount of time preparing my first invention disclosure. I can show them how to have it done in three or four hours instead of days and days.”

At some point, a formal application is presented to the U.S. Patent Office. “We have wonderful patent attorneys,” Dindl said. “John DiScala, he's just done a wonderful job for me on the patent applications that he filed for me. He really had to fight for the polymer case cartridge patent for me. The patent examiner was really tough on it. It took John about a year of going back and forth with the patent examiner to get it approved, but he did it. I'm very grateful for that. That's the biggest invention of my career. I really wanted to see a patent issued for it, and he made sure that it happened.”

While receiving a patent bestows some measure of credibility, persuading others to provide money to develop the invention further is another hurdle. There is only so much money to go around. Typically, there is also competition for limited resources.

“I think it helps with the funding proposal process if I can state that an invention disclosure has been submitted, or even better if the invention committee has already agreed to file a patent application, or still better a patent application has been filed and we have patent pending status,” Dindl said

“But generally, this is a very minor consideration,” Dindl noted. “The potential utility of the invention really drives the likelihood of a proposal being funded.

“Every situation is different. Some inventions don’t take long to develop into a usable product, while others take years. I’ve had inventions undergo a 20 year development and Type Classification (satisfies requirements for production), only to get cancelled before production and fielding starts. Other inventions have been fielded quickly under an Urgent Fielding effort.”

There are certain things that can be done during the early research and development phase with internal funding by an organization such as the Armaments Center, Dindl said.

“That's a fairly limited amount of money--the early tech-based level R&D,” Dindl explained.

Within the Armaments Center, there may be more than one potential path to acquire funding. “It's the folks that have money that you pitch your idea to, and if it fits within what they're looking for, then you have a pretty good shot. Then, if it doesn't, you try somewhere else.”

Beyond the limited local funding, another level of funding and development is possible if an invention and its capabilities is designated a “requirement,” a seemingly low-key term that nonetheless carries weighty significance in the realm of military acquisition: It elevates the prospects of having an invention developed to the point that it may eventually get fielded.

“It's not until you get a formal requirement approved that the funding levels really jump up to where you can just do a lot of things,” Dindl explained.

The U.S. Government Accountability Office, in a June 2017 report, defines requirements as follows: “Requirements are the operational performance attributes necessary for the acquisition community to design a proposed system and establish an acquisition program baseline. This includes key performance parameters and key system attributes that guide a program’s development, demonstration, and testing.”

Requirements are typically generated by the Army’s Training and Doctrine Command, which includes various Centers of Excellence that focus on various capability areas, such as aviation, cyber, fires, sustainment and others.

“It's a big effort to prepare a written requirement in the military,” Dindl noted. “It's a big process, and I understand the reluctance for anybody wanting to undertake that because it’s typically a multi-year effort to get a formal requirement approved.”

Yet, even during those times when success seems within reach, when the pieces and processes and protocols seem finally to align, the unexpected can intervene.

“Invention development can get sidetracked at a lot of points during the process,” Dindl noted.


TechLink is the authorized transfer partnership intermediary for the U.S. Department of Defense and Department of Veterans Affairs. Here is its link regarding the coolant cartridge: