Defense Media Network

The Evolution of the M134D Minigun

One iconic weapon system with deep historical ties to special operations forces (SOF) is the multi-barreled “Gatling gun.” Originally applied on fixed-wing and rotary-wing aircraft platforms, the “Miniguns” have evolved and expanded to a variety of naval surface and ground vehicle platforms within the SOF community.

The primary Minigun weapon system employed in SOF air, naval, and ground applications today is the 7.62 mm M134D weapon system family manufactured by Dillon Aero, in Scottsdale, Ariz.

“John Gatling came up with the Gatling gun back in the 1860s,” explained Chris Dillon, vice president at Dillon Aero. “That design was successful in its time, but then died around the turn of the [20th] century when the machine gun came out. But sometime after the machine gun came out – before or right around World War I – somebody actually took an early generation electric motor and put it on a Gatling gun. They tried it, thought it was great, didn’t know how to feed it, so put it away.”

Dillon m134d minigun

A Dillon M134D on board a Canadian CH-146 Griffon helicopter over Afghanistan. Photo courtesy of Dillon Aero

“After World War II, when the speeds of aircraft started to exceed 450 to 500 miles an hour, people realized that existing weapons didn’t produce enough concentrated fire to put a dense enough shot group into a chunk of airspace in a timely fashion,” he added. “So the government contracted with General Electric to create what was eventually called the M61 [Vulcan] Gatling gun. That is a 20 mm cannon that is in every F-16, F-18, and F-15 flying today.

“After the success of the M61, they generated lots of different designs: 30 mm guns, 25 mm guns, and during the Vietnam War, with government money, they produced the original GAU-2A and GAU-2B [7.62 mm] versions of the weapon system,” Dillon continued. “That was originally done with U.S. government money, and they produced some 10,000 guns throughout the war.”

“Sometime around 1975 they basically stopped producing any support spares for the weapon system,” Dillon stated. “That was fine, because the Army had a massive amount of inventory, which they managed to burn through over the next 10 years or so, so that essentially by 1985 there was very little spares support left in the inventory. Rapidly, units that were using the weapons found themselves unable to maintain them, so that by about the 1990s there were really only two units left using the weapon system: TF [Task Force] 160 [which evolved into the 160th Special Operations Aviation Regiment (SOAR), the “Night Stalkers”] and some of the Navy’s Special Boat Units.”

According to Dillon, the company began working with the weapon system in the ’89-’90 time frame, “completely unaware of what the military was doing with it.” Dillon Aero’s efforts began with the acquisition of a tractor-trailer load of Miniguns and spares from what he described as “a friendly foreign user.”

“So we started shooting them. And what we found in shooting them was that they didn’t work worth a darn. We tried and tried and tried to get them to shoot continuously and successfully without failures. But what we did not know at the time was that the surplus we had bought was actually worn out stuff,” he said.

“That turned out to be a blessing in disguise,” he said, “because when we got fed up with these things, we came to the conclusion that we were either going to box them up and forget about it or we were going to fix it. We chose to fix it. And in the process of solving all the problems that we discovered with the guns, we ended up fixing innate problems the gun had in its design. And knowledge of that effort eventually leaked its way back to TF 160.”

Dillon continued, “At this time – about ’94-’95 – the 160th was acquiring spares that TACOM [U.S. Army Tank-automotive and Armaments Command] was soliciting from industry. So you had these small production runs and some of it went to small ‘mom and pop shops’ that had a really hard time producing the parts to the [blueprints]. What happened was that the Army unintentionally began procuring spares that basically didn’t work. And those spares were getting into the inventory system and mixed with the existing spares that were good – essentially polluting the spares pool. The result was that guys ‘at Regiment’ [the 160th SOAR] would be putting spares in the gun and it wouldn’t work. Then they would pull another spare out, put it in the gun, and it would work. Nobody was sure what was going on but they knew they had an unreliable system now: a system that was essential to their work yet was unreliable.

“They were on the verge of removing the weapon system from the inventory completely,” he acknowledged. “And if Regiment had dropped it, it would have been done for history. But it was just a complete fluke of timing that we happened to be doing what we were doing when they were coming to this conclusion. And somebody heard through the grapevine about what we were doing here in Arizona. Then one day we got a phone call saying they had heard about what we were doing and inviting us to Fort Campbell [Ky.] to show them our products.”

A Special Warfare Combatant-craft Crewman (SWCC) mans his GAU-17 Minigun during live-fire patrol training along the Salt River in northern Kentucky, Aug. 25, 2007. Miniguns now serve on board a wide variety of SOF platforms. U.S. Navy photo by Mass Communication Specialist 2nd Class Jayme Pastoric

A Special Warfare Combatant-craft Crewman (SWCC) mans his GAU-17 Minigun during live-fire patrol training along the Salt River in northern Kentucky, Aug. 25, 2007. Miniguns now serve on board a wide variety of SOF platforms. U.S. Navy photo by Mass Communication Specialist 2nd Class Jayme Pastoric

Dillon and his father quickly arrived with a delinker – a component that separates cartridges from ammunition “belts” and feeds them into the gun housing – and some other parts that were soon being test fired on Fort Campbell ranges.

“Over the course of the next year or so, we started getting orders for delinkers from the 160th, and that produced a need and a cause for us to start improving every other component in the system where we saw issues: bolt design; housing design; barrel design; et cetera. I think the contracts started coming in ’97-’98 and then by about 2000, 2001, 2002, every year we were introducing new products for the Minigun. I calculated it out once: From 1997 to 2001, I think we were doing something like 25 to 30 products a year for it.”

In the fall of 2001, the company was working on a new bolt design that provided significantly increased performance and improved service life. Dillon observed that the attacks of 9/11 provided the company’s customer base with an urgent need to get the new bolt design certified and fielded.

“By 2002, we had basically improved every component on the weapon system, and we thought, ‘What the heck. Let’s just make new guns.’ So we made a batch of guns just because we wanted to make a batch of guns, and they got purchased very quickly by the government. In fact, Regiment bought some of the first batch of guns, and we did not know that they had been actively looking this entire time for a replacement for the Minigun to be the regiment’s standardized weapon system. Meanwhile, TACOM bought several of the guns, going through their approvals process, which took about a year, and then certifying it as the latest version of the minigun: M134D.”

Dillon observed that the weapon has been through many iterations in its development life, including: 6,000 round (per minute) rate of fire; 2,000 and 4,000 round selectable rate of fire; AC power sources; and the current DC power configuration.

“With all the design changes and modifications and improvements, we ended up with the M134D, which has a steel housing and steel rotor at the core of the weapon system.”

However, with the 160th SOAR as its primary customer base, continuing emphasis was placed on weight reduction.

MRAP minigun

Special Forces ODA Team 1236 prepares to roll out for a medical engagement in Khakrez, Afghanistan. The MRAP vehicle is armed with a remote weapons system mounting a Minigun. Photo by Tech. Sgt. Carmen A. Cheney, USAF

“They’re an aviation outfit, so for them, weight is premium,” Dillon said. “Everything they do revolves around how heavy the aircraft is, how much fuel they have, and how many passengers and weapons they can carry. So we saw an opportunity to significantly reduce the weight of the Minigun by altering design and materials.”

Early weight-saving investigations included the development of a titanium housing and a titanium rotor, which lowered the weapon weight for a new M134D-T (titanium) design from 62 pounds to 41 pounds.

“The titanium housing was great,” he added, “except that after about 500,000 rounds fired – which, in machine gun language is a very large number – a portion of it would start to wear out. Again, 500,000 rounds is a massive lifespan. Most machine guns have a life of about 40,000 rounds before you change them out. But we decided that we could save a whole lot of money and only gain 1 pound back by changing the housing back to steel. And you went from the decremented life of 500,000 rounds back up to the normal life of 1.5 million rounds.

“That process eventually resulted in the M134D-H, which is a hybrid version of the weapon that we have now,” he said, adding that the hybrid version is “on every 160th platform.”

“And it’s not all Minigun stuff,” he noted. “The Minigun requires a bunch of other stuff. It requires specialized mounts. It requires specialized ammunition-handling systems. And you have to get proficient at making that stuff or the gun doesn’t go very far … So we put a considerable amount of effort in figuring out how to make good mounts – initially for aircraft and then boats and then vehicles.”

Other growth areas include ammunition-handling systems and efficient magazine designs.

“These different knowledge bases started coming together to build a bigger picture and allow us to do greater stuff,” he stated. “We have now gone so far as to make weapons mounts for every combat deployed helicopter in the world – with the exception of some stuff done by the Chinese.”

M134d-h minigun

A crew member mans his M134D-H as an MH-47G Chinook from the 160th SOAR arrives at Simmons Army Airfield, Fayetteville, N.C., with participants from the 2012 U.S. Army Special Operations Command Capabilities Exercise, April 23, 2012. U.S. Army photo by Sgt. 1st Class Michael R. Noggle

“For quite a while the M134D was almost the exclusive property of ‘the aviation side of the house,’” he recalled. “Then the Navy had some on some of their small specialized boats. That was about ’03, ’04, ’05. Then about ’05 some of the Special [Forces] Groups started to procure some weapon systems for uses on Humvees, working in conjunction with Navy Crane [Naval Surface Warfare Center-Crane].”

Dillon related a combat vignette relating to early ground applications of the M134D by an Army Special Forces Group in Iraq.

“When they first got the guns in Iraq, the group started rolling out on their usual routines,” he said. “Prior to this they had been getting into engagements every single day. But then the Miniguns showed up. The engagements started but the enemy suddenly got hammered. Very quickly the engagements stopped, and the users were picking up radio chatter from the enemy calling, ‘What the hell was that? There’s a new weapon. Get out.’ This went on a few times and suddenly that group was not getting engaged anymore. Everybody else was, but not them. Guys rolling out ahead of them were hit. They rolled out and nothing happened. Guys rolled out behind them and got hit.

“Well, the group was there to fight,” he continued. “So they started putting it together – along with reports of captured pictures of HMMWVs with something that looked like a Minigun on top of it and guidance ‘not to [mess] with this guy.’ So they started trying to use coverings to hide the fact that they had Miniguns and get back into the fight. And it was all because the enemy quickly figured out that this thing was much more effective than average weapon systems.”

As an aside he added, “Meanwhile, some of the ‘Regular’ Army units who saw that happening started taking PVC pipe, painting it black, and zip-tying six sections around their barrels. Because they didn’t want to get shot at anymore. They were getting sick of it. And the Minigun has that kind of psychological effect.”

Based on those sorts of battlefield experiences, Dillon said that the weapon “has found its way to a lot of different ground platforms and continues to do so. I won’t say this is a categorical statement – but it is a ‘near categorical’ statement – that it is starting to look like every new vehicle program that is being put out for solicitation has Minigun as one of the requirements.”

Along with the weapons themselves, the company also manufactures turret systems that are being rolled into some of the solicitations.

A walk through the company’s facilities provides a glimpse at the scope of potential applications for the M134D and other company developments. Passing through a hangar containing a half-dozen fixed- and rotary-wing aircraft platforms, Dillon walked toward a nearby building.

“A few years back we ended up buying this vehicle down here because we were doing a little bit of vehicle work, which then turned into a bunch of vehicle work, which then took over a whole section of the building,” he said.

Parked in front of the building was a Land Rover that the company purchased as a stock U.N. excess platform and has since been modified as a “gun truck” with a cage, turret system, and other alterations.

“That’s actually the very first design we came up with, and we’ve gotten such positive response that we’ve stuck with it,” he explained. “The turret system that you see on the top is what we’re calling the MMC – Multi Mission Capable – turret system. It’s got a Minigun magazine on top. A lot of effort went into designing that ground applications magazine, too. And if you pull that magazine out you can drop a ‘sub-tray’ into it and put a .50-cal up there. You can pull that sub-tray out and put Mk. 19 cans or 7.62 mm up there. So it’s the same mount system that handles all the weapon systems.”

Inside the building was a demo “heavy SUV” Convoy Escort Vehicle that Dillon has equipped with a roof hatch and stowed Minigun that can be deployed in less than 3 seconds.

The fabrication shop also featured a surplus Land Rover being modified to easily drive on and off a CH/MH-47 series helicopter.

“Everybody has had a hard time consistently hitting the height bogie,” he said. “But when this is all said and done, it will be a ‘gunned up, roll off, and be ready to fight within 60 seconds’ vehicle that will have everything from the gun truck on it but will be able to drop down to less than 68 inches – significantly below the height requirements.”

This article was first published in The Year in Special Operations: 2013-2014 Edition.


Scott Gourley is a former U.S. Army officer and the author of more than 1,500...

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