The Gyrojet was an early attempt at a hand-held, rocket projectile firearm. Manufactured in the 1950s, it fired 13mm (later reduced to 12mm due to U.S. 50-caliber restrictions) self-propelled rocket shells. The gun was not very successful; it was nearly useless at close range as the projectiles hadn't accelerated enough to do much damage, and wasn't very accurate at longer range. The missiles were heavy, though, so a hit at medium range would do severe damage. Now extremely rare.