Make: MB Associates (MBA)

Model: 137

Serial Number: None.

Year of Manufacture: 1962-1963

Caliber: .49 Gyrojet, a .49 caliber spin stabilized rocket cartridge composed of four part solid rocket fuel.

Action Type: Semi-Automatic with Fixed Magazine

Barrel Length: 6 3/4"

Sights / Optics: The front sight is a blade integral to the left portion of the frame at the muzzle. The rear sight is a short, square-notch integral to the frame at the rear, each portion of the frame forms half of the sight.

Stock Configuration & Condition: The grip is integral to the frame, appearing as a checkered panel on each side. There is some light scuffing on some of the raised edges of the checkering. Overall, the grips are in Fine condition.

Type of Finish: Gold, controls left in the white.

Finish Originality: Original

Bore Condition: Rather than a traditional barrel, the frame has a hollow tube with integral guide rails to stabilize the rocket as it accelerates out of the gun. The "barrel" shows signs of limited, if any use, rates 10/10.

Overall Condition: This pistol retains about 92% of its metal finish. The finish is thinning at some edges. There are scattered light nicks, scuffs and scratches, mostly not through the finish. The screw heads are sharp. The markings are clear. Overall, this pistol is in Very Good-Fine condition.

Mechanics: The action functions correctly. We have not fired this pistol. As with all used firearms, a thorough cleaning may be necessary to meet your maintenance standards.

Box, Paperwork & Accessories: None.

Our Assessment: Who doesn't want a hand-held rocket launcher? MB Associates thought the answer would be "everyone!". Robert Mainhardt and Arthur Biehl met while working together at Aerojet-General Nucleonics, working on their AGN-201 nuclear reactor. While MBA was profitable in their manufacture of chaff and flare devices for aircraft, the Gyrojets would have to be considered something of a passion-project.

Their earliest efforts at a miniature rocket-launcher were for a disposable pistol to drop to Vietnamese peasants, similar to the GM Liberator concept from WWII. A later project would fire a cluster of small rockets to clear minefields. There was an odd project with tiny pin-sized rockets fired using an adapter on a standard cartridge firearm, ostensibly for dispatching sentry dogs, but appearing more useful for delivering chemical/biological agents to an individual without their permission.

Given these projects, the Gyrojet pistols and carbines seem almost pedestrian. The cartridge design actually hearkens back to one of the earliest self-contained cartridges, the rocket-ball. With all of the propellant contained in the cartridge, a fixed firing pin is ignited when the hammer strikes the front of the cartridge. Once ignited, the burning propellant comes out of angled ports at the rear of the cartridge, spinning the entire assembly to stabilize it as it accelerates down the bore. Unlike traditional cartridge firearms, the projectile continues to accelerate for up to 20 yards after leaving the bore, reaching its highest velocity not at the muzzle, but when the propellant is exhausted. Quieter than a traditional cartridge, the firearm could be made extremely light as it did not have to contain much pressure, and it would work under water (in theory).

The earliest Gyrojet firearms, such as this Model 137 were made to fire a .49 Caliber cartridge and didn't have a traditional barrel, but stabilizing rails build into the launch tube. The Later Mark I pistols were chambered for a 13mm cartridge with a more barrel-like tube, but reverted to the .49 caliber (12mm) after the GCA went into effect.

This example is a Model 137 and has a desirable gold finish. With about 1,900 Gyrojets produced in all of their pistol and carbine configurations, any example is a good find. This will make a wonderful addition to any collection, and if you can source any ammunition it ought to a blast to shoot. Please see our photos and good luck!