2mm Kolibri

The 2mm Kolibri (also known as the 2.7mm Kolibri Car Pistol or 2.7×9mm Kolibri) is the smallest commercially available centerfire cartridge, patented in 1910 and introduced in 1914 by Franz Pfannl, an Austrian watchmaker, with financial support from Georg Grabner. It was designed to accompany the Kolibri semi-auto pistol or single shot pistol, both marketed as self-defense weapons.

The name is derived from the colibri or hummingbird, which is among the smallest of birds.

Background
The cartridge weighs 5.3 grams (82 grains), measures 3 millimeters (0.12 in) at its widest point, and 11 mm (0.43 in) from the base of the primer to the tip of the bullet. The cartridge is headspaced on the mouth of the case. The bullet itself masses 0.2g (3 grains), and is estimated to have a normal muzzle velocity of 200 m/s, resulting in a muzzle energy of 4.0J (3 ft-lbs).

The round was not well accepted. The 2mm Kolibri's small size makes handling and loading individual cartridges difficult, and the bullet itself is fairly weak, with literature at the time suggesting the round was capable of penetrating only 10 - 40 mm of pine board. The round also suffers some accuracy issues, since the technology of the time was incapable of applying rifling to the bore of such a small caliber, resulting in no spin on the bullet.

The series, and most weapons by Franz Pfannl, were discontinued in 1938.

As with the related firearm series, this gun is now a collector's item with about 1000 ever produced. It is notable for being the smallest centerfire cartridge ever produced.