This Cartridge of the week was mentioned in another post so I researched it and thought it would be a good one to make the list.

The 2.7 Kolibri is the smallest factory produced centerfire cartridge ever made. Introduced in 1914 it was chambered in two different guns. One a semi-auto of blow back design and the other a single shot pistol of the commonly called "parlor type"  The bullet only has approximately 650 to 700 fps muzzle velocity and a WHOPPING 3 foot pounds of energy at the muzzle. Considering the bullet only weighs 3 grains and is .105 to .108 inches in diameter, you could not expect much more from it. For a contrast it makes our .25 acp look like a magnum because the 25 acp has 73 foot pounds of energy at the muzzle.  Can you imagine trying to reload one of these rounds??? I reload the 25 acp and I have a little pair of tweezers that I have bent in a half circle on each side to hold the little .25 dia. bullet because my fingers are to big and get in the way when I try to run the press ram up. There are no statistics on what type or size of animal this cartridge would be suitable for hunting but my guess would be a very small mouse or perhaps a large cockroach.