Gyrojet

Gyrojet
The Gyrojet carbine, and the rifle at the National Firearms Museum
Type	Small arms (rocket)
Place of origin	United States
Service history
Used by	See Users
Production history
Designer	Robert Mainhardt Art Biehl
Manufacturer	MBAssociates
Variants	See Variants
Specifications
Weight	0.88 lb (0.40 kg)
Length	10.88 inches (27.6 centimetres)
Barrel length	5 inches (13 centimetres)
Cartridge	Mark I- 13 mm rocket Mark II- 12 mm rocket
Caliber	Mark I- .51 caliber Mark II- .49 caliber
Action	Blow-Forward
Rate of fire	60 RPM Select Fire (Assault Rifle variant)
Muzzle velocity	very low, but increasing over trajectory to about 1250fps
Effective firing range	55 yards (50 m)
Feed system	6-round internal box magazine (Main Variants)
Sights	Iron sights

External image

Image of derringer model at handguns of the world

The Gyrojet is a family of unique firearms developed in the 1960s named for the method of gyroscopically stabilizing its projectiles. Rather than inert bullets, Gyrojets fire small rockets called Microjets 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 1,250 feet per second (380 m/s) at 30 feet (9.1 m). The result is a very lightweight weapon.

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.

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 .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, 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 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.