The Gyrojet: A Science Fiction Fantasy from the 1960s

The history of firearms is, to an extent, one of hard-won incremental improvements with the occasional quantum leap in technology. While there have been such moments of brilliance in design conception, they are generally few and far between.

Such ideas, when they take hold, can be revolutionary. The invention of the bullet containing payload and propellant in one handy package, spiral rifling inside the barrel for increased accuracy, semi-automatic action and ejection of spent cartridges to speed up reload times: these are such moments.

Not all such ideas are as brilliant however, and the history of the gun is one containing many, many mistakes. There are a multitude of forgotten firearms, some of which go in a frankly bizarre direction, often for the sake of innovation as much as in pursuit of genuine improvements.

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These design changes tend to result in a loss in reliability above all. The Lemat “grapeshot revolver” for example seems brilliant: a revolver pistol with a separate central barrel for buckshot. But such an additional came with reliability problems and it remains a curio, consigned to history. 

However it is amongst these firearms that the future can sometimes be glimpsed. Although failures at the time, sometimes the new ideas may just point the way towards what the far future of personal combat may look like.

Such is the case with the Gyrojet, the gun that fired microrockets.

A Flawed Experiment

The Gyrojet is not, in fact, a single gun but rather a family of firearms developed in the 1960s. There was to be a Gyrojet pistol, a carbine and a rifle, a machine gun and even an exotic needlegun, known as the Lancejet.

The guns were the brainchild of a man named Robert Mainhardt, and the rifle and carbine even made it to production. From the outside they appeared largely conventional, but their internal workings and design were entirely different from conventional firearms.

These guns were named for the way their projectiles were gyroscopically stabilized, and it is in these rounds that the magic can be found. The Gyrojet weapons fired tiny, armor-piercing rockets at up to 60 rounds per minute.

A normal gun relies on a single explosion within the firing chamber to propel a bullet. This is straightforward and reliable but comes with a few drawbacks. For a start, once you have fired the round it has all the energy it is going to get. It is never faster than the point it leaves the barrel.

Bullets are therefore necessarily small, compact and aerodynamic. But a rocket fired in the same way can continue to build energy after it has been fired, potentially allowing for much more damage to be caused to the target.

There are other serious advantages to this technology, too. The rifling on the inside of a normal barrel, which is a major factor in a gun’s accuracy, also slows the bullet as it is fired, damaging the gun every time it is fired and slowing the bullet, robbing it of impact energy.

The Gyrojets did not require such rifling, as they carry their own propulsion and rely on other methods for stability. This meant that the Gyrojet guns had smooth barrels, meaning that the projectile left with more energy and could do more damage. Removing the need for precise rifling also meant the gun could be more simple, with less to go wrong.

So how was accuracy achieved, then? Well, as the Gyrojet fired the rocket exhaust of the projectile was directed into four ports angled such that it would spin in flight, much like the firework known as a Catherine Wheel. The rocket only fired for a fraction of a second, but it was enough to produce an accurate and powerful projectile from a barrel that was little more than a smooth tube.

The design also meant that recoil was significantly reduced, allowing for the guns to be fired with greater accuracy still and with less fatigue to the user. The barrel length, normally so important to accuracy, was also less relevant here, meaning the guns were unusually compact and portable.

The burn time of the microrocket, although very brief, was still enough to power it for some 18-20 m beyond the barrel and accelerate it to supersonic speeds. And there was nothing particularly unusual about the technology used to propel the projectile either: conceptually it was not really any more complex than a standard bullet cartridge.

So, why aren’t these guns of the future everywhere then? Well, there were several problems but basically the guns didn’t work as advertised: they were unreliable and inaccurate in practice.

The tiny ports on the side of each projectile could easily become blocked, leading to wildly inaccurate and diverging flight paths. This weapon was first tested in the Vietnam War where conditions on the ground proved too much for the new technology: ports would become fouled and humidity would get into the fuel inside, resulting a projectiles simply failing to fire.

In addition the gun, even when it could be fired, was woefully inaccurate. Many factors were cited for this, but it boiled down to uneven combustion of the internal fuel, machining errors which resulted in some ports being bigger than others, and the direction the microrocket chose to travel in the all-important 20 meters beyond the barrel.

The frustrating thing about these shortcomings however was that they were not fundamental, but rather due to the engineering limitations of the time and the fact that these guns were essentially still prototypes. With enough development, there was no reason these could not have become forerunners to a brave new world of rocket propelled handweapons.

Robert Mainhardt and his investors certainly saw the potential in the idea, but these early failures meant that the idea was dropped in favor of simpler, proven and cheap technologies, namely bullets. In desperation, Mainhardt even turned to Gene Roddenberry, creator of Star Trek, to see if he had any interest in featuring the futuristic weapon in his sci-fi series.

Roddenberry preferred ray guns. And so the Gyrojet was consigned to history, one of the great might-have-beens.

Top Image: The Gyrojet, one of the great what-if moments in firearm innovation. Source: Joe Loong / CC BY-SA 2.0.