Hi Tom..the weapon was used a few times to good effect
..took out an NVA SOG hunter squad..the fierce backblast
was an issue and it could be unstable...some blurb below
explains soem of the issues..cheers Ged
www.gringo40s.com 
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.[9] 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.[10]
About 1000 of the "Rocketeer" model pistols were produced; a few saw service in the Vietnam War, and were featured in the James Bond book and movie You Only Live Twice, the Matt Helm film Murderers' Row, as well as one of The Man from U.N.C.L.E. novels, The Monster Wheel Affair. 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 pushed 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 claimed 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 100 ft/s (30 m/s) at 1 foot (30 cm) instead of the calculated 20 ft/s (6.1 m/s). The testers suggested that the (secret) manufacturing process was designed to achieve this effect.[8] However, independent analysis of those testers' own published data shows that their conclusions were incorrectly calculated. The projectile's acceleration actually started out low and continually increased over the bullet's measured flight.[11]
