The Bell UH1 Huey helicopters proved that the concept of air cavalry was feasible during the
first days of the Vietnam War. However, their M60 machine guns were not powerful enough to defend
the aircraft from the concentration of enemy fire when approaching a landing area or taking off from
a hot evacuation zone. And what’s worse, they quickly overheated and were prone to failure.
General Electric then came in and introduced its M134 rotary machine gun,
which quickly earned the nickname of ‘The Minigun.’
The gun proved so successful at its role that the Army and Air Force began to fit it
into other aircraft, such as the Cobra, which had two Miniguns, and the AC130,
which was armed with four and had an astonishing rate of fire of over 14,000 rounds per minute.
Chambered in a 7.62-millimeter cartridge and with no risk of overheating,
the Minigun quickly became the ultimate weapon used to clear the Vietnamese jungles.
Gatling Gun
The American Civil War is widely considered one of the most important conflicts
that marked the dawn of a new age of warfare. During the gruesome conflict in the late 1800s,
there was a drastic change that merged the old and new ways of conducting warfare.
It was then that one of the battlefield’s most powerful weapons ever used against
infantry emerged: the Gatling gun. Developed by Richard Jordan Gatling,
it was a rapid-fire, spring-loaded, hand-cracked gun that had a revolutionary rate of fire of over
600 rounds per minute at a time when soldiers could fire two or three rounds per minute.
The gun was centered on a cyclic multi-barrel design
that helped cool and synchronize the firing-loaded sequence without overheating issues, but the real
innovation was that each barrel fired a single shot, ejected the spent cartridge, and loaded a
new round to be fired again in the next cycle. The revolutionary gun would also be heavily
employed by European colonial armies in Africa and Asia during the Zulu Wars,
the Boxer Rebellion, and the American conflicts of Cuba and the Philippines.
Then, in 1893, Gatling exchanged the hand-cranked mechanism
and fitted the gun with an electric motor for automatic fire.
This invention bolstered the gun’s rate of fire to an astonishing 3,000 rounds per minute.
Despite its groundbreaking nature, the US Army did not show interest in the improved electric-powered
Gatling gun, as it was more expensive than recoil and gas-operated machine ones.
Richard Gatling eventually went bankrupt, as his rotary gun was forgotten and was
not even used during World Wars 1 and 2. Nevertheless, with the broad introduction
of jet aircraft during the post-war, the US Army would look back into its history
to reintroduce Gatling’s cannon with an impressive array of upgraded features.
Project Vulcan
Following the end of World War 2, the US Army Air Forces became a separate branch of the Army
and reintroduced itself as the United States Air Force or USAF.
During the war, the Air Force had learned that German and Japanese aircraft had better
range than its fighters due to the use of cannons as their main armament. As such,
the branch immediately began considering the introduction of more powerful aircraft guns
for use against the first fighter jets. Aircraft such as the P47 Thunderbolt or
the P51 Mustang had to get close to the enemy to fire their .50-caliber M2 Browning machine guns,
while other aircraft, such as the P61 Black Widow and the P38 Lightning,
used the effective 20-millimeter Hispano cannon, which had a low fire-rate against jet aircraft.
Consequently, the Air Force turned to Gatling’s Civil War-era rotary gun.
Gatling’s improved gun needed an external electric power source to
rotate the barrel assembly, but fortunately for the Air Force,
if there was one thing that turbojet-powered aircraft did not lack, it was electric power.
Both the Air Force and the Army believed that a rotary cannon inspired by Gatling’s design
would result in an improved rate of fire over previous single-barrel cannons,
and in 1946, the Army awarded General Electric a contract for Project Vulcan.
The program’s objective was to develop a six-barrel rotary gun
capable of firing up to 7,200 rounds per minute. General Electric and the armed forces settled
in for a 15-millimeter caliber for the new gun, and the first prototype, dubbed T45,
was fired for the first time in 1949, achieving a rate of fire of 2,500 rounds per minute.
As more prototypes and calibers were tested, the fire rate eventually increased,
with the USAF settling for a 20-millimeter cartridge that provided outstanding muzzle
velocity, range, accuracy, and damage.
This prototype variant, known as the T171, was eventually redesignated the M61 Vulcan
and was introduced as the main armament of the Lockheed F104 Starfighter.
Although the linked ammunition was prone to misfeed, the problem was worked out,
and the 20-millimeter M61 Vulcan cannon quickly became the standard armament of USAF aircraft.
What’s more, the Vulcan cannon would eventually make its way to rotary-wing aircraft as the
war in Vietnam escalated in the 1950s and American intervention seemed inevitable.
A Necessary Replacement
Prior to the French withdrawal from Vietnam,
the US supplied the French Army with helicopters and other aircraft for use against the Viet Minh.
Meanwhile, US advisors took note of the operational usage of helicopters
and the benefits they could provide to the mobility of ground forces if adequately used.
When it was time for the Americans to finally set foot in the Vietnamese countryside in 1965,
they did so aboard the Bell UH1 Iroquois, also known as the Huey.
The use of this helicopter, which would become another synonym of the Vietnam War, proved that
the concept of air cavalry was more than feasible. However, despite the effectiveness of the Hueys
while carrying soldiers and supplies into battle across the dense jungle,
they quickly became the object of enemy small-arms fire and rocket-propelled grenades.
Although the Hueys were armed with the lethal single-barrel M60 machine guns used by ground
forces, these were not enough to effectively suppress fire when landing or taking off from
a hot landing zone with enemies pouring out by the hundreds from the jungle foliage.
The M60 was a powerful machine gun, but firing it without interruption
led to cartridge jams and overheating.
With this in mind, the Army and Air Force decided to develop a weapon with a reliable
fire rate that could decimate the enemy and help clear landing zones with proper firepower.
It was then that General Electric stepped up and decided to develop a gun that could be
mounted on Hueys with shocking effect. As the company assessed its options,
it began exploring the possibilities of producing a more compact version of its
booming 20-millimeter M61 Vulcan rotary cannon. The aim was not just to reduce the Vulcan’s
scale but to increase its rate of fire without any overheating issues.
The result was the XM134 rotary gun, a six-barrel, air-cooled, electrically-driven rotary machine gun
that the US Army designated as M134 while the USAF dubbed it GAU 2A or GAU17A.
Whichever the case, GE's scaled-down version of the Vulcan was quickly nicknamed the Minigun.
The M134 Minigun
The Minigun weighed 85 pounds and had a barrel length of 558 millimeters and an overall length
of 801 millimeters with its firing mechanism and trigger. It could fire up to 6,000 rounds per
minute without overheating, but 4,000 was the adequate rate to prevent overheating.
Meanwhile, the rounds had a muzzle velocity of 2,800 feet per second
and an estimated range of 3,280 feet. Army and Air Force personnel were equally
baffled by the Minigun’s performance, as the 7.62-millimeter cartridge and
the tremendous rate of fire easily tore apart the jungle canopies in Vietnam.
The Minigun’s feed system was simple. A disintegrating M13 linked belt or
linkless feed made sure it never ran out of rounds from its ammunition box.
Also, the firing action stripped the cartridge from the belt
and fired it through the designated barrel, subsequently ejecting the casing and link belt.
When the gunner depressed the Minigun’s trigger, the feed was automatically shut off from the bolt
and barrel assembly to keep ammunition from being brought into the host-spinning barrels. This was
automatically done to keep both the ammunition and the barrels cool for the following action.
Finally, the gun was mounted on Hueys alongside its external powerpack to test it during combat.
The weapon excelled at its purpose, as there was no way out for the enemy
once a Minigun operator pushed the trigger to clear a landing zone.
It was not just an effective device to suppress or support fire but also for
raining terror on all the Vietnamese who left the foliage and made themselves an open target.
An attempt to make the Minigun portable for ground forces was also made, but it was impossible
due to the indispensable external power pack. Nevertheless, the Army experimented with the XM214
Microgun, which was an even smaller version of the Minigun chambered in a 5.56-millimeter cartridge
used by the M16 rifle, but it was quickly discharged due to frequent technical problems.
Still, the impressive combat performance of the Hueys mounted with Miniguns
led the Army and the Air Force to incorporate it into other types of aircraft for use in Vietnam.
Tours of Duty
Given the success of the Bell UH-1 Iroquois, the Army mounted Miniguns on several rotary-wing
aircraft such as the Bell AH-1 Cobra, the Hughes OH-6 Cayuse, and the OH-58 Kiowa.
The Miniguns were also mounted on different types of gun pods,
ranging from the Army’s M18 pods with over 1,500 rounds of ammunition to the USAF’s SUU11A ones.
The most lethal out of all the helicopters was the AH1 Cobra, which was specifically designed
to work as an escort for the Hueys. It proved lighter, faster, and more harmful than the UH1.
The Cobra was fitted with two Miniguns, which drastically multiplied its firepower,
bringing a combined rate of fire of over 8,000 rounds per minute.
And if that wasn’t enough, the Cobra also carried 19 rockets and M129 40-millimeter
rocket launchers. Few Vietnamese survived when a pack of Cobras was sent to clear an area
prior to the arrival of the Hueys. Following the success of the Cobra
with its Miniguns, the Army fitted the OH6 Light Observation Helicopter with two of them.
Despite its smaller size and vulnerability, the Loach and its Miniguns became essential
when operating with Cobras, as they pinpointed the enemy’s location
from above the jungle canopy before the Cobras arrived to rain hell upon the enemy.
The Minigun also excelled with close air support aircraft and became the essential armament
of the Cessna A-37 Dragonfly and the Douglas A-1 Skyraider.
However, the first American gunships, such as the AC-47 Spooky, the AC-119, and the AC130,
truly took the Minigun’s reign to another level.
Mounted on specialized gun pods, or Minigun modules,
these gunships carried up to four miniguns that became crucial in saving the lives of soldiers and
Marines that required immediate close air support. Firing more than 16,000 rounds per minute, entire
fields showed the magnitude of the devastation before they managed to break a friendly perimeter.
Today, almost 60 years after its introduction, the Minigun is still in use by the US military
and other armies around the world, and has gone through several innovations
that have increased its firepower, range, accuracy,
and cooling systems, turning it into a more lethal weapon than it already was.
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