Gyrojet
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The Gyrojets were a family of unique firearms developed in the 1960s. Firing small rockets rather than inert bullets, they had little recoil and didn't require a heavy barrel to resist the pressure of the combustion gasses. The result was a very lightweight weapon with excellent ballistics. Long out of produciton, 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.
Robert Mainhardt and Art Biehl joined forces to form MBAssociates, or MBA, in order to develop Biehl's armor-piercing rocket rounds. Originally developed in a 13 mm caliber, the cartridges were self-contained self-propelled rockets. Spin stabilization was provided by angling the four tiny rocket ports rather than by forcing the projectile through a rifled barrel. Combustion gasses released within the barrel were vented through the vent holes in the barrel. Due to the properties of the rocket, with continued acceleration after it left the barrel, the Gyrojet had poor short-range power, but improved dramatically with distance. After about 75 yards (70 m) the motor would burn out, at which point the pistol-sized round had about 50% more power than the common Colt .45.
A family of weapons was designed, including a pistol, carbine, "rifle" and squad-level light machine gun. However only the pistol and carbine were built. The space age-looking carbine versions were tested by the 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.
Early tests showed the Gyrojet to be more accurate than conventional firearms, as expected due to the flatter trajectory. However, later testing showed that accuracy was very poor. It appears the difference was due to the quality of the ammunition; a small manufacturing flaw in later production runs partially blocked one of the exhaust ports, creating assymetrical 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 one was featured in a James Bond book and movie. At about the same general size as the Colt .45, the Gyrojet was considerably lighter at only 22 ounces (625 g). The weapon was cocked by sliding a lever above the trigger forward to pull a round into the gun, which sprung 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 to fire again. 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.
It appears there is nothing inherently wrong with the concept, other than inadequate initial firing velocity. A round can actually be stopped if a finger or even piece of cardboard is held directly at the end of the barrel. This flaw is fatal, however, for a firearm intended to be used at relatively close range.
As previously mentioned any rocket velocity was a product of thrust, and time (i.e. distance). At close ranges this led to blocked rockets simply stopping and burning out relatively harmlessly, making it useless for close-range self-defence. On the other hand since velocity actually increased over some distance the projectiles trajectory did not suffer as great a ballistic drop compared to conventional ammunition, greatly simplifying aim at longer ranges, an advantage for offensive military uses.
The Gyrojet principle was also examined for use in survival flare guns, and a similar idea was explored for a grenade launcher. 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 signalling, with flares available in several colors, white, green, blue, and red. Known as the gyrojet flare, the A/P25S-5A could penetrate overcover in trees and had an effective altitude of over 1500 feet(300 meters). It's rounded nose projectile was designed to riccochet through trees and clear an over canopy of branches. It was quite effective. It came with a bandalier of six flares.
Some fiction like the Cyberpunk 2020 supplement Deep Space consider Gyrojets as weapons of choice in space, thanks to its lack of recoil.
Another interesting note is that in the science fiction continuity of Warhammer 40,000 an almost identical concept is used (bolter weapons), despite being almost 38,000 years into man's future.
[edit] External links
- Gyrojet
- The Deathwind Project - updated versions of the original concept
- Rocket Pistols In Vietnam - Includes David Kirschbaum's recollections of actually carrying and using one in combat. (this link submitted by David Kirschbaum himself)
