Gyrojet
Encyclopedia
The Gyrojet is a family of unique firearm
s developed in the 1960s named for the method of gyroscopically
stabilizing its projectiles. Gyrojets fire small rocket
s, rather than inert bullet
s, which have little recoil and do not require a heavy barrel to resist the pressure of the combustion gases. Velocity on leaving the tube was very low, but increased to around 1250 feet per second (381 m/s) at 30 feet (9.1 m). The result is a very lightweight weapon with excellent ballistics.
Long out of production, today they are a coveted collector's item with prices for even the most common model ranging above $
1,000. They are, however, rarely fired; ammunition, when available at all, can cost over $100 per round.
A family of Gyrojet weapons was designed, including the pistol
, the carbine
and a rifle
, as well as a proposed squad-level light machine gun
and the Lancejet
, however only the pistol and carbine were built. The space age
-looking carbines and an assault rifle
variant with a removable grip-inserted magazine were tested by the US Army, where they proved to have problems. One issue was that the vent ports allowed the humid air into fuel, where it made the combustion considerably less reliable. The ports themselves could also become fouled fairly easily, although it was suggested that this could be solved by sealing the magazines or ports.
Versions of the Gyrojet that were tested suffered from poor accuracy, cumbersome and slow loading, and unreliability (at best, a 1% failure rate was suggested; users quote worse figures, with many rounds that misfired the first time but later fired). Possibly these disadvantages could have been overcome in time, but the technology did not offer enough advantages over conventional small arms to survive.
When spin stabilization was chosen for the Gyrojet, the compact electronics used in today's smart bullet
s were not available. Both the cost and size of inertial navigation equipment have reduced greatly since a Gyrojet launcher was reviewed in "Guns and Ammo Magazine" in 1965.
A firearm's rifled barrel must be manufactured to high precision and be capable of withstanding extremely high pressures; it is subject to significant wear in use. The Gyrojet rocket is fired through a simple straight, smooth-walled tube of no great strength.
Accuracy is increased by spinning
the projectile. This is achieved for a bullet by being forced against spiral rifling
grooves in the barrel. A rocket does not have enough initial energy to allow stabilization this way. Spin stabilization of the Gyrojet was provided by angling the four tiny rocket ports rather than by forcing the projectile through a rifled barrel. Combustion gases released within the barrel were vented through vent holes in it. Spin stabilization is limited in accuracy as a targeting technique by the accuracy with which one can point the launching tube and the accuracy with which the orientation of the projectile is constrained by the tube. The technique requires the shooter to have a line of sight to his target. For this reason the Gyrojet has been made obsolete by modern miniature inertial guidance equipment which suffers from none of these limitations. Advantages of the Gyrojet design over a hypothetical Inertially guided small arms rocket launcher are that, if ammunition for both were manufactured in sufficient quantity, the Gyrojet ammunition could be less expensive than ammunition incorporating an IMU
and Gyrojet ammunition is of a smaller caliber than is likely to be produced as a rocket with a current technology IMU, considering the size of highly miniaturized IMU components now available.
The rocket leaves the barrel with low energy, and accelerates until the fuel is exhausted at about 60 feet (20 m), at which point the rocket has a velocity of about 1250 feet per second (FPS), slightly greater than Mach one, with about 50% more energy than the common .45 ACP
round. While test figures vary greatly, testers report that there was a sonic crack from some rounds, but only a hissing sound from others, suggesting that the maximum velocity varied from slightly below to slightly above Mach 1.
In 1965, the manufacturer of the pistol claimed 5-mil accuracy (about 17 MOA, or about 4.5 inches at 25 yards), worse than conventional pistols of the time. However in later tests accuracy was very poor; the difference seems to have been due to a manufacturing flaw in later production runs which partially blocked one of the exhaust ports, creating asymmetrical thrust that caused the projectile to corkscrew through the air.
About 1,000 of the "Rocketeer" model pistols were produced; a few saw service in the Vietnam War
, and were featured in a James Bond
book and movie You Only Live Twice
, as well as one of The Man from U.N.C.L.E.
novels. At about the same general size as the Colt M1911, the Gyrojet was considerably lighter at only 22 ounces (625 g) as the structure was mostly made of Zamac, a zinc alloy. The weapon was cocked by sliding forward a lever above the trigger to pull a round into the gun; the lever sprang back when the trigger was pulled. The lever hit the bullet on the nose, driving it into the firing pin. As the round left the chamber, it pulled the lever forward again to recock it. The pistol lacked a removable magazine; rounds had to be pushed down from the open "bolt" and then held in place by quickly sliding a cover over them on the top of the gun. Reloading quickly was impossible.
Tests in 2003 found that the acceleration, rather than being constant, started at a high value and decreased, leading to velocities at close range which were not as low as expected, about 100fps at 1 foot instead of the calculated 20fps. The testers suggest that the (secret) manufacturing process was designed to achieve this effect.
At longer range the velocity increases, so that the projectiles' trajectory does not drop as much as conventional ammunition, simplifying aim at longer ranges.
created a new legal term, the destructive device. Under the new law, any weapon firing an explosive-filled projectile over a half-inch in diameter was considered a destructive device and required paying a tax and obtaining a license. The registration process was changed several years later, but in the interim, MBA created the legal Gyrojet Mark II, firing a .49 caliber rocket.
Derringer pistol with an upper barrel chambered for the Gyrojet round.
. The emergency-survival flare version (A/P25S-5A) was used for many years as a standard USAF issue item in survival kits, vests, and for forward operations signaling, with flares available in white, green, blue, and red. Known as the gyrojet flare, the A/P25S-5A came with a bandolier of six flares and had an effective altitude of over 1500 feet (500 m). Its rounded-nose projectile was designed to ricochet through trees and clear an over canopy of branches.
and was planned to be used, but wasn't in You Only Live Twice
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...
s developed in the 1960s named for the method of gyroscopically
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
stabilizing its projectiles. Gyrojets fire small rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s, rather than inert bullet
Bullet
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...
s, which have little recoil and do not require a heavy barrel to resist the pressure of the combustion gases. Velocity on leaving the tube was very low, but increased to around 1250 feet per second (381 m/s) at 30 feet (9.1 m). The result is a very lightweight weapon with excellent ballistics.
Long out of production, today they are a coveted collector's item with prices for even the most common model ranging above $
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
1,000. They are, however, rarely fired; ammunition, when available at all, can cost over $100 per round.
History
Robert Mainhardt and Art Biehl joined forces to form MB Associates, or MBA, in order to develop Biehl's armor-piercing rocket rounds. Originally developed in a .51 caliber, the cartridges were self-contained self-propelled rockets with calibers ranging from .49 and 6mm to 20mm.A family of Gyrojet weapons was designed, including the pistol
Pistol
When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder. Typically, pistols have an effective range of about 100 feet.-History:The pistol...
, the carbine
Carbine
A carbine , from French carabine, is a longarm similar to but shorter than a rifle or musket. Many carbines are shortened versions of full rifles, firing the same ammunition at a lower velocity due to a shorter barrel length....
and a rifle
Rifle
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...
, as well as a proposed squad-level light machine gun
Machine gun
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....
and the Lancejet
Underwater firearm
An underwater firearm is a firearm specially designed for use underwater by frogmen.Underwater firearms were first conceived during the Cold War during the 1960s and 1970s as a way to arm frogmen, and remain in arms inventories today.-Design:...
, however only the pistol and carbine were built. The space age
Space Age
The Space Age is a time period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events. The Space Age is generally considered to have begun with Sputnik...
-looking carbines and an assault rifle
Assault rifle
An assault rifle is a selective fire rifle that uses an intermediate cartridge and a detachable magazine. Assault rifles are the standard infantry weapons in most modern armies...
variant with a removable grip-inserted magazine were tested by the US Army, where they proved to have problems. One issue was that the vent ports allowed the humid air into fuel, where it made the combustion considerably less reliable. The ports themselves could also become fouled fairly easily, although it was suggested that this could be solved by sealing the magazines or ports.
Versions of the Gyrojet that were tested suffered from poor accuracy, cumbersome and slow loading, and unreliability (at best, a 1% failure rate was suggested; users quote worse figures, with many rounds that misfired the first time but later fired). Possibly these disadvantages could have been overcome in time, but the technology did not offer enough advantages over conventional small arms to survive.
When spin stabilization was chosen for the Gyrojet, the compact electronics used in today's smart bullet
Smart bullet
Smart bullet is a term that has been used to describe several theoretical and prototype bullets. The "smart" part comes from the bullet doing something other than simply following its given trajectory, e.g. turning, speeding up, slowing down, sending data, etc....
s were not available. Both the cost and size of inertial navigation equipment have reduced greatly since a Gyrojet launcher was reviewed in "Guns and Ammo Magazine" in 1965.
Design
The inherent difference between a conventional firearm and a rocket is that the projectile of a conventional firearm builds up to its maximum speed in the barrel of the firearm, then slows down over its trajectory; the rocket continues to accelerate as long as the fuel burns, then continues its flight like an un-powered bullet. A bullet has maximum kinetic energy at point-blank range; a rocket has maximum kinetic energy immediately after its fuel is expended. The burn time for a Gyrojet rocket has been reported as 1/10 of a second by a Bathroom Reader's Institute book and as 0.12 seconds by "The 'DeathWind' Project."A firearm's rifled barrel must be manufactured to high precision and be capable of withstanding extremely high pressures; it is subject to significant wear in use. The Gyrojet rocket is fired through a simple straight, smooth-walled tube of no great strength.
Accuracy is increased by spinning
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
the projectile. This is achieved for a bullet by being forced against spiral rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
grooves in the barrel. A rocket does not have enough initial energy to allow stabilization this way. Spin stabilization of the Gyrojet was provided by angling the four tiny rocket ports rather than by forcing the projectile through a rifled barrel. Combustion gases released within the barrel were vented through vent holes in it. Spin stabilization is limited in accuracy as a targeting technique by the accuracy with which one can point the launching tube and the accuracy with which the orientation of the projectile is constrained by the tube. The technique requires the shooter to have a line of sight to his target. For this reason the Gyrojet has been made obsolete by modern miniature inertial guidance equipment which suffers from none of these limitations. Advantages of the Gyrojet design over a hypothetical Inertially guided small arms rocket launcher are that, if ammunition for both were manufactured in sufficient quantity, the Gyrojet ammunition could be less expensive than ammunition incorporating an IMU
Inertial measurement unit
An inertial measurement unit, or IMU, is an electronic device that measures and reports on a craft's velocity, orientation, and gravitational forces, using a combination of accelerometers and gyroscopes. IMUs are typically used to maneuver aircraft, including UAVs, among many others, and...
and Gyrojet ammunition is of a smaller caliber than is likely to be produced as a rocket with a current technology IMU, considering the size of highly miniaturized IMU components now available.
The rocket leaves the barrel with low energy, and accelerates until the fuel is exhausted at about 60 feet (20 m), at which point the rocket has a velocity of about 1250 feet per second (FPS), slightly greater than Mach one, with about 50% more energy than the common .45 ACP
.45 ACP
The .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...
round. While test figures vary greatly, testers report that there was a sonic crack from some rounds, but only a hissing sound from others, suggesting that the maximum velocity varied from slightly below to slightly above Mach 1.
In 1965, the manufacturer of the pistol claimed 5-mil accuracy (about 17 MOA, or about 4.5 inches at 25 yards), worse than conventional pistols of the time. However in later tests accuracy was very poor; the difference seems to have been due to a manufacturing flaw in later production runs which partially blocked one of the exhaust ports, creating asymmetrical thrust that caused the projectile to corkscrew through the air.
About 1,000 of the "Rocketeer" model pistols were produced; a few saw service in the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
, and were featured in a James Bond
James Bond
James Bond, code name 007, is a fictional character created in 1953 by writer Ian Fleming, who featured him in twelve novels and two short story collections. There have been a six other authors who wrote authorised Bond novels or novelizations after Fleming's death in 1964: Kingsley Amis,...
book and movie You Only Live Twice
You Only Live Twice (film)
You Only Live Twice is the fifth spy film in the James Bond series, and the fifth to star Sean Connery as the fictional MI6 agent James Bond. The film's screenplay was written by Roald Dahl, and loosely based on Ian Fleming's 1964 novel of the same name...
, as well as one of The Man from U.N.C.L.E.
The Man from U.N.C.L.E.
The Man from U.N.C.L.E. is an American television series that was broadcast on NBC from September 22, 1964, to January 15, 1968. It follows the exploits of two secret agents, played by Robert Vaughn and David McCallum, who work for a fictitious secret international espionage and law-enforcement...
novels. At about the same general size as the Colt M1911, the Gyrojet was considerably lighter at only 22 ounces (625 g) as the structure was mostly made of Zamac, a zinc alloy. The weapon was cocked by sliding forward a lever above the trigger to pull a round into the gun; the lever sprang back when the trigger was pulled. The lever hit the bullet on the nose, driving it into the firing pin. As the round left the chamber, it pulled the lever forward again to recock it. The pistol lacked a removable magazine; rounds had to be pushed down from the open "bolt" and then held in place by quickly sliding a cover over them on the top of the gun. Reloading quickly was impossible.
Tests in 2003 found that the acceleration, rather than being constant, started at a high value and decreased, leading to velocities at close range which were not as low as expected, about 100fps at 1 foot instead of the calculated 20fps. The testers suggest that the (secret) manufacturing process was designed to achieve this effect.
At longer range the velocity increases, so that the projectiles' trajectory does not drop as much as conventional ammunition, simplifying aim at longer ranges.
Gyrojet MkI
Aside from a few Gyrojets tested by the United States Military, most Gyrojets were sold on the commercial market starting in the mid-1960s. These were Mark I Gyrojets, which launched a .51 caliber rocket, and ammunition was costly to produce and buy.Gyrojet MkII
In 1968, the U.S. Gun Control Act of 1968Gun Control Act of 1968
The Gun Control Act of 1968 , by president Lyndon Johnson, is a federal law in the United States that broadly regulates the firearms industry and firearms owners...
created a new legal term, the destructive device. Under the new law, any weapon firing an explosive-filled projectile over a half-inch in diameter was considered a destructive device and required paying a tax and obtaining a license. The registration process was changed several years later, but in the interim, MBA created the legal Gyrojet Mark II, firing a .49 caliber rocket.
Gyrojet Assault Rifle
Assault rifle variant with M16 type ergonomics tested by the US Army. This variant had full auto capability and a removable grip inserted magazine. To increase ammo capacity, it's possible this platform was chambered in the 6mm calibre.Gyrojet Derringer
Image
Derringer pistol with an upper barrel chambered for the Gyrojet round.
Gyrojet Flare Launcher
The Gyrojet principle was also examined for use in survival flare guns, and a similar idea was explored for a grenade launcherGrenade launcher
A grenade launcher or grenade discharger is a weapon that launches a grenade with more accuracy, higher velocity, and to greater distances than a soldier could throw it by hand....
. The emergency-survival flare version (A/P25S-5A) was used for many years as a standard USAF issue item in survival kits, vests, and for forward operations signaling, with flares available in white, green, blue, and red. Known as the gyrojet flare, the A/P25S-5A came with a bandolier of six flares and had an effective altitude of over 1500 feet (500 m). Its rounded-nose projectile was designed to ricochet through trees and clear an over canopy of branches.
Gyrojet Lancejet
An underwater firearm variant of the Gyrojet called the Lancejet was considered for use by the United States military, but the inaccuracy of the weapon eventually removed it from consideration.Gyrojet Pepperbox pistol
An experimental twelve barrel Gyrojet pepperbox type pistol was made that was used in Murderers' RowMurderers' Row (film)
Murderers' Row is a 1966 American comedy-spy-fi film starring Dean Martin and very loosely based upon the Matt Helm spy novel Murderers' Row by Donald Hamilton, which was published in 1962....
and was planned to be used, but wasn't in You Only Live Twice
You Only Live Twice (film)
You Only Live Twice is the fifth spy film in the James Bond series, and the fifth to star Sean Connery as the fictional MI6 agent James Bond. The film's screenplay was written by Roald Dahl, and loosely based on Ian Fleming's 1964 novel of the same name...
Gyrojet Conversion gun
A prototype gun that converted from a pistol to a rifle. Had a foling wire stock and a screw on barrel. Chambered in the 13mm cartridge format.Users
Although the Gyrojet was not officially adopted by any government, a few privately bought examples were used during the Vietnam War.External links
- Gyrojet
- The Deathwind Project - updated versions of the original concept
- Rocket Pistols In Vietnam - David Kirschbaum's recollections of actually carrying and using one in combat