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The Gyrojet: In This Case, It Is Rocket Science

In the late 20th century (I feel old just typing that), Americans had been involved in multiple world wars and conflicts and were looking for a new frontier. That frontier, however, looked quite different from the days of the Old West. Rather, they set their sights on outer space, both physically and metaphorically. Americans landed on the moon in 1969 and even though not everyone could travel to space, they dreamed about it in movies, television, and novels. So, it’s no surprise that the space race would impact other industries. 

In the firearms industry, both military and civilian manufacturers were trying to develop more durable firearms with less weight and recoil, by incorporating new materials. The most well-known and popular firearm from this time period, the AR-15, was originally manufactured by Armalite — a subsidiary of Fairchild, an aeronautics manufacturer for sky and space. And while some manufacturers focused on the firearm construction itself, others focused on ammunition. In 1958, David Dardick patented a triangular round or “tround,” which was essentially a projectile encased in a triangular polymer shell. He built a firearm for this type of ammunition, which saw some experimentation by the U.S. government in testing under Project SALVO. However, the tround ultimately was a misfire. 

gyrojet muzzle
Multiple angles of the Gyrojet Mark 1 Model B from the Cody Firearms Museum.

Speaking of unsuccessful products, in this same time frame, two engineers, with a history of working on the Manhattan Project tried their hand at firearms technology. In 1960, Robert Mainhardt and Arthur Biehl formed MB Associates (MBA). While the company was involved in many industries, they developed a particularly fascinating space-agey weapon — a handheld rocket, if you will — the Gyrojet. 

Finjets and Lancejets

In 1958, the Defense Advanced Research Projects Agency (DARPA) was created to facilitate R&D projects for the military. Several people working for the Agency were former colleagues of Mainhardt and Biehl. On April 1, 1960, MBA was formed and shortly after they worked to apply a pre-Gyrojet concept to DARPA. At the time of the formation of MBA, the Agency was looking for a cheap and disposable firearm that could be used by the Vietnamese against the Vietcong — a similar concept to the Liberator Pistol from World War II. MBA submitted the idea of a handgun that could fire tiny rockets. These rockets were known as Finjets. It was a fin-stabilized .12-caliber rocket less than 2 inches in length. However, despite experiments with materials, accuracy was terrible. So bad that when firing a salvo of 24 rockets at a time, these finjets only had a 50/50 chance of one rocket hitting an 18-inch circle at 100 yards — not great odds if you’re a betting man. As a result, the Finjets never got off the ground. MBA was undeterred however and tried to create a larger rocket, .25 caliber and 6 inches long with an explosive charge, known as a “Lancejet.” This was meant for clearing mine fields. However, it was plagued by accuracy issues as well. 

gyrojet round

In 1961, MBA began working on the first concept of a Gyrojet. The biggest design difference was devising a way to utilize rocket exhaust in a way that would spin the rocket in flight, like the stabilizing effect of rifling on a normal projectile. 

A Historian’s Attempt at Describing Rocket Science

Let me make something abundantly clear, I’m not a rocket scientist. As a historian, sometimes I even struggle with basic math. But I’m great at reading and researching. I read several descriptions of how the Gyrojets operate and from those works by people smarter than I, I have deduced the following: 

The rocket has a hollow metallic cartridge case filled with propellant and a primer in the center of the base. However, the base had angled openings so that when fired, the projectile can rotate and accelerate — without the need of rifling used in traditional barrels.

Gyrojet  Mark 1 Model B  from the Cody Firearms Museum.
Gyrojet Mark 1 Model B from the Cody Firearms Museum.

 Like most rockets, these are propelled by thrust generated by a burning propellant. The rocket burns for approximately 1/10 of a second and reaches a velocity of 1,500 feet per second at about 60 feet from the muzzle, spinning 19,000 revolutions a minute. Since there’s no pressure buildup inside the weapon, there really is no recoil. Additionally, the firing sequence doesn’t produce a bang, but a whooshing sound.

MBA decided on a .49-caliber rocket initially after testing for “accuracy” or as much as they could achieve. The original sketch from one of their engineers paired the ammunition with a single-stack, six-rocket-capacity-magazine handgun. Unlike a traditional pistol, the hammer is in front of the rockets, instead of behind. After the trigger is depressed, the hammer hits the front of the rocket and pushes it into a firing pin, holding it in place long enough to build up thrust. As the rocket moves out of the barrel, the process starts over. 

gyrojet projectile

An interesting component to the early design was that it lacked a barrel. As there was no pressure buildup, the earliest guns didn’t technically need it. They had guide ribs attached to the frame. However, in testing, it was found a smoothbore barrel aided accuracy. 

The Variations

The first production gyrojet was the Model 137 in .49 caliber. Only about 45 pistols were made. They quickly moved on to the Mark 1 Model A. This pistol was chambered in 13 mm (.51 caliber) and was considered more accurate than its predecessor. Other than that, the two firearms were very similar. 

gyrojet reciever
Gyrojet Mark 1 Model B from the Cody Firearms Museum.

While MBA had hopes for large government contracts, the inaccuracy of the firearms coupled with their novelty made the engineers think the Gyrojet would have better luck on the collector market. They marked them experimental and created wooden cases. They made about 100 Mark 1 Model A pistols. 

The next version was the Mark 1 Model B. The main difference with this version was that a slide was put over the loading area rather than a hinge. The market for these guns was both collectors and shooters. Within this scope, the Model B saw several variations in carbines, types, and finishes. About 1,100 were made. 

Gyrojets didn’t just come in handgun form. They were made as long-guns as well, which were basically the pistols with longer barrels and wooden stocks. The first Mark 1 Model A carbine was made to look like an M16. And the Mark 1 Model B carbines both came in a sporter and military-style versions.

gyrojet rocket

After the Gun Control Act of 1968 initially ruled the .51-caliber smoothbore Gyrojets as “destructive devices” — they later changed that designation — MBA reverted back to the .49 caliber and created a useless light rifling to make the Bureau of Alcohol, Tobacco, and Firearms happy. It was known as the Mark 1 Model C, and about 600 were made. 

In the end though, the only successful Gyrojets were flares developed to be used in the Mark 1 Model B “Survivor” pistol. This became the Model 201 Gyrojet flare, and these versions are still in use today. 

Real-World Applications

Like so many real-world inventions, sometimes they seem much cooler on the big screen. The Gyrojet appeared in the 1967 James Bond film You Only Live Twice. It also appeared in Life Magazine as a story on the “Deadly Zip Gun for the Missile Age.” Unfortunately, not everything you read and see is true. 

It was true though that the Gyrojet was ingenious, but it was the only project MBA was involved in that wasn’t profitable. Like many experiments from the time period, the
Gyrojet is a retro space-age reminder of firearms development over the past 70 years, but hey, at least collectors got a jump on that market right from the start! 


GyroJet

Caliber: 13mm
Length: 9.875 inches
Barrel Length: 6.75 inches
Rate of Fire: 60 rpm
Capacity: 6 rounds
Action: Blowback


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