.25 ACP
The smallest common centerfire — historically important and fun to collect, but modern micro .380s do its job far better.
Family
Handgun
Introduced
1905
Origin
John Browning, FN, Belgium
History
Browning created the .25 ACP around 1905 to give vest-pocket pistols a centerfire cartridge with more reliable ignition than tiny rimfires. Millions of Baby Brownings, Colt Vest Pockets, and their imitators chambered it through the 20th century. It survives today almost entirely in the collector world.
What it's used for
Iconic platforms
FN Baby Browning, Colt Model 1908 Vest Pocket, Beretta 950 Jetfire, and Raven-era pocket autos.
Common load types
FMJ almost exclusively, with rare hollow point offerings.
Reference only — not loading data, not ballistics advice, and KitID links to no ammunition sellers. Know your local law before you buy anything that goes bang.