9mm and .380 ACP cartridges — both popular choices for self-defense rounds — have the same diameter, but a 9mm round is longer. The .380 ACP round is cheaper and easier to handle and conceal, while the 9mm is more powerful overall. The rounds can both be used in revolvers and autoloaders, but are not interchangeable with one another.
The .380 ACP cartridge (also called a 9mm Browning) was introduced in 1908 by Colt as a self defense weapon. The .380 ACP cartridge is rimless and straight-walled. The 9mm (9×19mm Parabellum) cartridge was introduced in 1902 by German weapons manufacturer DWM for their Luger semi-automatic pistol.
Although some foreign police use the .380 as a primary weapon, American police and military forces see it as a backup weapon, as it lacks the power of similar-sized pistols like the 9mm and .38 Special. Its primary use remains that of self defense for civilians, as its small size allows for easy concealment and it can hold a relatively high amount of rounds.
The 9mm Luger has become the popular caliber for US law enforcement agencies due to the availability of compact pistols with large magazine round capacity using this caliber. It is also a popular self-defense cartridge for civilians where permitted.
.380 ACP cartridges are currently more expensive than 9mm cartridges. This is due to the high supply of 9mm cartridges from various manufacturers, and a surge in demand for the less ubiquitous .380 ACP ammo. Due to their smaller size and simpler construction, .380 pistols are generally cheaper than 9mm weapons. A compact budget pistol can be found for under $200. 9mm pistols are more expensive, and most budget guns start closer to $300.
Power and Performance
The power of .380 ACP guns is noticeably below that of 9mm weapons. The maximum velocity (1000 FPS) and energy ratings (148 MPa) of the .380 are about 40% below a 9mm, both using JHP+P type loads. While this means the .380 is less destructive, it also performs with less of a recoil, making it a more accurate weapon in short-range, rapid-fire use.
The 9mm has a maximum velocity of 1,400 FPS and an energy rating of 2465 foot pounds, and is by all measures a more powerful cartridge. The downside of this additional power (when compared to the .380) is a stronger recoil, lowering overall accuracy in rapid-fire situations. The video below tests the performance of the .380 ACP against that of the 9mm.
The fact that the .380 cartridge fires with less force gives it the advantage of being more accurate, particularly in rapid-fire situations, as there is less force to contend with while attempting to keep the shots on target. In single-shot or long-range scenarios, it mostly comes down to user skill.
The .380 has less penetration power than the 9mm round: 9 inches for the .380 versus 13 inches for the 9mm.
Recoil and Size
Being the shorter, less powerful round, the .380 generally has less recoil than the 9mm cartridge, although this varies with the characteristics of the gun used. A heavier weapon means less recoil.
.380 cartridges are better if concealment is a top priority. The rounds are shorter and less powerful, meaning the pistols that fire them can be smaller and easier to conceal than when using 9mm rounds.
Choosing the Right Cartridge
The bottom line is, .380 ACP round is cheaper to use and easier to handle, while the 9mm is more powerful in every metric. Choosing one over the other depends on whether your priority is power (the 9mm) or ease of use and concealment (.380 ACP).
The .380 was a variant of the .32 ACP Pocket Hammerless pistol released by Colt in 1903. The only modifications to the gun were to the bore size and magazine. Despite the name, the guns do have a hammer, but it is concealed inside the housing, which prevents the hammer from snagging on clothing and makes the gun easier to withdraw from concealment.
Designed with military use in mind, the 9mm Luger initially had lead core. But during WWII, it was made using iron core jackets to conserve lead. By 1944, normal copper core cartridges were produced.
The .380 ACP by John Browning was introduced in 1908 by Colt and was marketed as a self defense weapon. It was designed with a relatively weak bolt thrust for early blowback pistols which lacked barrel locking.
The 9mm Luger was designed by George Luger from his earlier 7.65X21mm Parabellum. In 1902 he presented it to British Small Arms Committee. In 1903 he presented 3 prototypes to the US Navy. It was adopted by the German Navy in 1905 and the German Army in 1906. Designed with military use in mind, initially the 9mm Luger was lead core. But during WWII to conserve lead, it was made using iron core jackets. By 1944, normal copper core cartridges were produced.