The world's smallest, commercialized pistol should be Swiss Mini Gun, which is a very interesting name, because M134 gatling's name is also Mini Gun. Swiss mini pistol is the world's smallest revolver certified by Guinness World Records. It fires a 2.34mm edge-fired bullet, with no propellant but only primary explosive, and the quantity is very small, which can only shoot through a few millimeters of pine wood. Shooting at a very close distance may still hurt the skin.
Another commercial mini pistol is the Hummingbird pistol from Germany. Its smallest version has a caliber of only 2.7 mm, and it is a central firing bullet, which can be said to be the smallest central firing bullet in the world. Hummingbird pistol is not a handicraft made to hit Guinness World Records. It is designed as a real self-defense pistol. Hummingbird pistol was patented in 191 and production began in 1914. Its name is Hummingbird, and it is the smallest pistol in the world, and it was indeed the smallest pistol in the world at that time.
The total weight of the 2.7mm bullet used in the hummingbird pistol is only 5.3g, and the total length is 11mm. The warhead weighs only .2 grams. Because it is extremely light, its muzzle velocity is about 2 meters per second, and its muzzle kinetic energy is only 4 joules. The bullet itself is not only small, but also very fragile, so be very careful in preservation. Moreover, with the technology at that time, it was impossible to process rifling in such a thin barrel, so the bullet could not rotate. According to the data at that time, the hummingbird pistol can only penetrate 1-4 mm thick pine wood, but it can still hurt bare skin at close range. Hummingbird pistols were discontinued in 1938, and about 1, were preserved, which is the best in the eyes of collectors.
In addition, there are some handicraft miniature pistols that fire other bullets, but they are very rare and can't be called commercial pistols.