The discontinued GyroJet Rocket Pistol is not truly a gun at all.
The GyroJet pistol is a pistol unlike any other in history. It shot rockets.
It is actually a miniature rocket launcher that is handgun sized. The GyroJet was an interesting note in the arms technology history book.
As incredible as it sounds, the GyroJet Rocket Pistol really did shoot miniature-sized rockets. This little weapon shot in a true semi-automatic fashion.
Downfalls of the GyroJet included the muzzle of the weapon velocity was lower and lethality was less than optimum. It took distance for the little rocket to get up to speed. Knock down power was just not there.
The GyroJet Rocket Pistol is now obsolete and discontinued. It is, however, an interesting lesson in modern weapon technology.