The Gyrojets were a family of unique firearms developed by MBA in the 1960s. Firing small rockets instead of bullets, they had almost no recoil and didn't require a heavy barrel to hold in the combustion gases. The result was a very lightweight weapon with excellent ballistics, and today they are a covetted collector's item.

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 13mm size, the rounds contained their propellant inside a stubby "cartridge" that stayed with the "bullet" in flight. Spin stabilization was provided by angling the four tiny rocket ports, the barrel simply provided the initial direction. This allowed the barrel to be very lightweight, and was in fact drilled full of holes in order to allow the rocket exhaust to escape. Due to the fact that the round continued to accelerate after it left the barrel, the Gyrojet had poor short-range power, but improved dramatically with range. After about 100 yards the motor burns 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 rocket 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. But the main problem was that the propellant was fairly smoky, and left a long black trail right back to the gun. In combat this would be fatal.

Reports of the gun in testing showed that the accuracy was very poor. However this contrasted with earlier reports that showed it to be more accurate than conventional arms. It appears the difference was due to the quality of the ammunition, and a small design flaw that potentially blocked one of the ports.

The Rocketeer pistol was produced to the tune of about 1,000 copies, and 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. The weapon was cocked by sliding a lever forward to pull a round into the gun, which sprung back when the trigger was pulled. The round leaving the gun would pull the lever forward again for semi-automatic action. One poor bit of design was the 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 basically impossible.

In 1968 new regulations in the US about civilian weapons being limited to .50" (12.5mm) forced a redesign down from the original 13mm caliber, and the company did not have enough money to finish the project before going bankrupt. Since then the pistols have become increasingly in demand for collectors, and the few remaining rounds of ammunition fetch prices of $20-$50 a round.

It appears there is nothing inherently wrong with the concept, and further development could result in an excellent weapon. The Gyrojet principle was also examined for use in survival flare guns, and a similar idea was explored for a grenade launcher.

External links

• Gyrojet
• The Deathwind Project - updated versions of the original concept