.45 ACP (left) and 9mm.
The .45 ACP is an American pistol cartridge that was a greatly scaled-up version of the 9x19mm Parabellum cartridge. A good way to tell the cases apart is the .45 is much more wider and dome-shaped than the 9mm, and is also a little bit taller.
It was the replacement of John McClane's 9mm Parabellum cartridge for his main sidearm when it changed from a Beretta 92FS to a SIG-Sauer P220.
History[]
The .45 ACP cartridge was designed by legendary firearms designer John Browning, who invented numerous repeating mechanisms such as fully automatic, lever action and bolt action, as well as numerous cartridges including .50 BMG and .380 ACP.