Gyrojet Firearms

deadSo I want to fire a rocket from my handgun, you got something for that?

The Gyrojet was an attempt to shake up the world of small arms cartridges, in the same way that the conversion to brass cased ammunition changed the firearms world. In the end the result of much testing and development was a unique round that was either doomed to fail or just way ahead of its time. Whatever the case may be the Gyrojet round and the firearms that bore them failed to attract the interest it need from the Army and Civilians.


In 1960, while the US and the then Soviet Union were embroiled in the epic space race two researchers were attempting to scale down rockets into something that could replace the brass cartridge firearms that were in use then and still used today. MBAssociates, or MBA, was founded by Robert Mainhardt and Arthur Biehl, the two wanted to create small rockets that would be useable in a variety of applications while remaining cost effective. Many who saw their work believed that it could not be done, however this only spurred the pair to continue their research.

Working together, Mainhardt and Biehl created several different designs for their idea of a rocket powered small arm. The initial concept was that of a self-contained projectile that would work with a more traditional rifled barrel. However this put a lot of stress on the firearm and proved to be too dangerous for the user to be turned into a small arms platform.

Pocket Rocket

Mark I Gyrojet
Image via Rock Island Auctions

Mainhardt and Biehl turned to Mainhardt’s friend Nick Minchakievich who changed the design to use retractable fins on the rear of the bullet, what he referred to as “finjet” to stabilize the bullet as it flew. The fins would create the gyroscopic stabilization necessary to create worthwhile accuracy, as opposed to the rifling of modern small arms. This solved the problem of scaling down the platform by removing the requirement for the receiver, barrel, and other parts from containing the pressures of the miniature rocket. However Minchakievich’s solution proved to be difficult to make, and cost prohibitive. Minchakievich then took the design, ditched the fins, and added diagonal holes to the rear of the design to direct the flow of the gasses out of the rear of the Gyrojet cartridge. These holes allowed the Gyrojet cartridge to be stable in flight, without the use of a rifled barrel, fins, or anything else. This seemed to be the best answer for the team at MBA.

Next was the firearm itself, the team had big plans for their design and wanted to see it used across a variety of platforms. First they introduced a handgun, the Gyrojet Mark I or, “Rocketeer”, fired a 13mm or .51 caliber version of the Gyrojet design. The pistol was comparable in size the 1911M1 in size, however it was far lighter compared to the 1911, weighing in at only 22 ounces, being constructed out of a zinc alloy, Zamac.

The pistol was a unique design, the magazine was integrated into the handle, meaning it could not be removed, and necessitated that it be fed from the top. However the magazine lacked feed lips and the rounds were held into place by a sliding cover. Furthermore the magazine also had a cut in the side so you could see the follower and the remaining rounds. The hammer was actually forward of the magazine, and not behind it, like the 1911 design, and had to be cocked on the first round, like the single action 1911. The firing pin was fixed and the hammer actually swung up, hitting the nose of the Gyrojet round, forcing the primer into the firing pin. The hammer actually helped to keep the round in place while it began its first few revolutions and gained enough thrust to push the hammer forward, re-cocking it, and allowing a new round to be set into place. A small external safety could be engaged after cocking the hammer to prevent the round from striking the firing pin, but it did not immobilize the hammer. The chamber actually was ported with a number of holes on each side to allow the gasses to escape with the barrel simply being little more than a tube. However to help with the accuracy of the firearm the barrel tube had to be milled to exacting tolerances, only three thousandths of an inch larger than the ammo it was firing.

Ian, at Forgotten Weapons took a look at one example of the Mark 1, Rocketeer at the Rock Island Auction company and you can see the video here.

About 1,000 of these Mark 1 handguns were made, and while some were given to the US Army for trials, most were sold to the civilian market. Almost everyone who bought one picked it up as a curiosity and the firearm never really took off as anything other than a display or conversation piece.

Mainhardt and Biehl both realized that the Gyrojet would never be a real success unless they were able to gain traction with the military and began to pursue military contracts. This resulted in the production of a carbine version of the platform as well as a M16 style assault rifle. The Gyrojet assault rifle was notable for its futuristic design, yet utilizing wood in its stock and handguard.

As the Gyrojet met with limited enthusiasm during its run in the 1960’s the Gun Control Act of 1968 forced MBA to develop the Mark II version of the Rockteer pistol. The original Mark I fell under the term “Destructive Device” of the 1968 Gun Control Act, and MBA developed the Mark II to use a .49 caliber, 12mm projectile, preventing it from being classified as a Destructive Device and subject to the stricter regulations.

The entire family of these firearms can be seen below, note that they each essentially have the same design in the action.

Gyrojet Firearms
Gyrojet Firearms – Image via Wikipedia

In addition to the four designs that were produced, a number of other designs were proposed or prototyped for the Gyrojet cartridge. This included an over under derringer that was ported at the rear of each barrel to allow the gasses to escape. At one point a .410 over under shotgun was converted to fire the round and was shown to Guns and Ammo in 1965.

A handheld flare launcher that was little more than a tube for a flare version of the Gyrojet cartridge. Several snub nosed versions of the Mark I, with three different barrel lengths. A spear gun utilizing Gyrojet propulsion referred to as the “Lancejet”. A twelve barrel pepper-box version that was supposed to appear on the film You Only Live Twice, but did not. A conversion gun that was supposed to convert from a pistol to a rifle, but the concept was abandoned. Finally, gold-plated versions in both sixteen and twenty-four karat gold were made.

The Mark 1 Rocketeer was often sold with a fine wood box that housed the pistol and 12 rounds of ammo for it. The case featured a bust of Robert Goddard, around whom the rounds were placed, as a nod to the father of modern rocketry.


We’re going to war

While the US Military found little reason to adopt the Gyrojet ammo and weapons over their current firearms the Gyrojet did manage to find its way to the battlefields of Vietnam. Officially the Army did not sanction the use of the Gyrojet as a side arm, however two members of the military fielded the firearm. David Kirschbaum carried one as a side arm and recalls his experience below.

Guns and Ammo Gyrojet
Image from

“As a Recon man I liked the weapon just fine: light, quiet, low-maintenance, and a hell of a punch. It was not silent, not like the true silenced .22 Hi-standards we often carried. But it was quiet, made a sort of “Psssssst!” It sounded like air escaping from a truck tire, maybe a half-second long. I fired it in camp several times, demonstrating it, never got any attention at all.”

“The biggest problem was the feed design. The rockets all pushed down into the handgrip of the pistol against a spring and follower. Then, while holding that last rocket down, you slid forward this cover on the top of the “receiver” that held them all in place. Fine and dandy if you were going to just shoot them. But shame on you if you had a misfire (although I never did) or a jam, which I did once.  To clear a jam, you’d have to slide back that slide, meanwhile holding all the rockets down with your thumb, and then they’d all want to come springing out! The design really REALLY sucked. It should’ve had a magazine like a regular automatic, instead of everything being integral. Impossible to clear in combat, and a real PITA to reload too.  Never the less, I liked the pistol just fine.”

Lt. Douglas G. Magruder, also had a Gyrojet Mark II with him in Vietnam, though it is uncertain if he used it as he gave his life in the war and the Gyrojet was among his returned personal belongings.

To Hollywood

While the design never caught on in the military it did see some limited success as a futuristic or spy weapon in a number of places in books and Hollywood. Nick Minchakievich took the Gyrojet to Gene Roddenberry who loved the design of the pistol, but rejected it for use in Star Trek, as he wanted a “Ray Gun”. The firearm featured not only the film but the James Bond book as well You Only Live Twice. It would make another appearance in a spy thriller novel The Man From U.N.C.L.E: The Monster Wheel Affair. Finally Matt Helm would use it in his movie, Murder’s Row.

Hand Cannon? Sort of.

The design of the round was strange to say the least, and not just radically different in design but performance as well. First and foremost, unlike most firearms the round actually increased in lethality the farther away from the barrel it got. The initial velocity of the round, like a rocket was zero, from there, as it traveled down the barrel, and even after leaving the barrel, the round continues to accelerate. Below did some calculations based off of previous tests by the DeathWind project on the Gyrojet Ammo to see the acceleration of the rounds and correct some errors with the previous tests conclusions.

Future Boy Calculations
Image via

Guns and Ammo also did a review of the Gyrojet in 1965, and while they were excited about the new developments, they noted that the design needed improvement. However they did record the bullet going at approximately 1250 feet per second with a 180 grain projectile. Yet, again has noted that it may be difficult to accurately measure the speed of the round due to the increase acceleration over the trajectory of the bullet, unlike a conventional one, and the constantly released gasses by the round interfering with chronograph equipment.

The Gyrojet was constructed out of a few parts, the shell of the round housed a small rocket pack inside of it. The shell was made from steel the help contain the high pressures of the Gyrojet round. The rocket pack was sealed off by a back plate with the angled ports to create the spin of the round. The back plate also housed the percussion primer that ignited the round. Retrieved examples that had been fired into a back stop by Guns and Ammo in 1965 seemed to do a decent job of deforming even for a round-nosed round. Wadcutter and longer rounds for the rifle and carbine models can also be seen in the Guns and Ammo review.

The fuel itself was a mixture similar to the nitrocellulose propellants used in gunpowder today and this was done for the ease of use, and to keep costs down. To prevent the rounds from becoming dangerous, a combustion inhibitor was added the outside of the rocket insert to keep the powder burning only inside of it.

Users loved that it was relatively quiet, hissing more than going bang, and while delivering comparable performance to a .45 ACP at terminal ranges. It was fun, but it had a number of issues that prevented it from taking off.


Houston we have a problem…

You Only Live Twice
The Gyrojet appeared in the movie You Only Live Twice – Image from Wikipedia

While utilizing many similar materials to today’s firearm cartridges, the rounds remained more expensive to produce, starting a $1.35 per round and only increasing in price from there. Additionally any defects in the machining of the critical vents at the rear of the round caused them to fly in accurately. Later runs of the ammo showed this issued frequently.

Testing of rounds was never able to make them more accurate than 30″ at 100 yards, no better than the small arms at the time, however practical testing showed that it was closer to seven feet at 100 yards. More recent testing by Small Arms Review showed a 50% hit rate in a nine foot target at 100 yards, however this was with old, degraded ammo. The design of the round made it difficult to seal and it was prone to failure due to moisture exposure or fouling of the vents on the back of the rounds. While the projected failure rate of the rounds was supposed to be %1, users reported it being much higher. Many rounds apparently would misfire at first but when struck again, would work.The original design of the Mark I and Mark II made it cumbersome to reload and clear malfunctions. Nothing kept the rounds in the magazine with the chamber open and they had to be manually held in place. Many of these issues could have been corrected with time. However the US Military and Robert Mainhardt refused to give Nick Minchakievich any more time to improve upon the design.


Unfired Gyrojet rounds are rare and cost in excess of $100 as of 2015, the design of the rounds makes them difficult to reload. Perhaps a gunsmith or ammo manufacturer could create a modern version of the round, however it would be difficult and time intensive to replicate, as everything would have to be built from scratch.

Available Firearms

Gryrojet firearms are exceedingly rare with only 1,000 of the Mark I’s ever being produced. The Mark II, Carbine, and Assault Rifle are even rarer. The average collector would have to get exceedingly lucky to even find one up for sale.

So it was a dud right?

Well sort of, while the Gyrojet design was a failure for its time, with the advent of “smart rounds” designers may have to look back on the work of Nick Minchakievich, Robert Mainhardt, and Arthur Biehl for inspiration on the design of bullets that adjust their trajectory mid-flight. Maybe the team at MBA was simply waiting for the technology to catch up to their ideas, whatever the case may be. For now, the Gyrojet is dead, may he rest in peace.

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