.45 ACP
| .45 ACP | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
.45 ACP cartridge full metal jacket | ||||||||||||||||||||||||
| Type | Pistol | |||||||||||||||||||||||
| Place of origin | United States | |||||||||||||||||||||||
| Service history | ||||||||||||||||||||||||
| Wars | World War I – present | |||||||||||||||||||||||
| Production history | ||||||||||||||||||||||||
| Designer | John Browning | |||||||||||||||||||||||
| Designed | 1904 | |||||||||||||||||||||||
| Produced | 1905–present | |||||||||||||||||||||||
| Variants | .45 ACP +P, .45 Auto Rim, .45 Super, .460 Rowland | |||||||||||||||||||||||
| Specifications | ||||||||||||||||||||||||
| Case type | Rimless, straight | |||||||||||||||||||||||
| Bullet diameter | .452 in (11.5 mm) | |||||||||||||||||||||||
| Land diameter | .442 in (11.2 mm) | |||||||||||||||||||||||
| Neck diameter | .473 in (12.0 mm) | |||||||||||||||||||||||
| Base diameter | .476 in (12.1 mm) | |||||||||||||||||||||||
| Rim diameter | .480 in (12.2 mm) | |||||||||||||||||||||||
| Rim thickness | .049 in (1.2 mm) | |||||||||||||||||||||||
| Case length | .898 in (22.8 mm) | |||||||||||||||||||||||
| Overall length | 1.275 in (32.4 mm) | |||||||||||||||||||||||
| Case capacity | 25–27.4 gr H2O (1.62–1.78 cm3) | |||||||||||||||||||||||
| Rifling twist | 1 in 16 in (406 mm) | |||||||||||||||||||||||
| Primer type | Large pistol LP (some makers are now using small pistol SP) | |||||||||||||||||||||||
| Maximum pressure (CIP) | 19,000 psi (130 MPa) | |||||||||||||||||||||||
| Maximum pressure (SAAMI) | 21,000 psi (140 MPa) | |||||||||||||||||||||||
| Ballistic performance | ||||||||||||||||||||||||
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The .45 ACP (Automatic Colt Pistol), also known as .45 Auto, .45 Automatic, or 11.43×23mm is a rimless straight-walled handgun cartridge designed by John Moses Browning in 1904, for use in his prototype Colt semi-automatic pistol. After successful military trials, it was adopted as the standard chambering for Colt's M1911 pistol. The round was developed due to a lack of stopping power experienced in the Moro Rebellion in places like Sulu. The issued ammunition, .38 Long Colt, had proved inadequate, motivating the search for a better cartridge. This experience and the Thompson–LaGarde Tests of 1904 led the Army and the Cavalry to decide that a minimum of .45 caliber was required in a new handgun cartridge.
The standard-issue military .45 ACP cartridge uses a 230 gr (15 g; 0.53 oz) round-nose bullet at approximately 830 ft/s (250 m/s) fired from a government-issue M1911A1 pistol. It operates at a relatively low maximum chamber pressure rating of 21,000 psi (140 MPa), compared to 35,000 psi (240 MPa) for both 9mm Parabellum and .40 S&W, which due to a low bolt thrust helps extend the service lives of weapons. Since standard-pressure .45 ACP rounds are subsonic when fired from handguns and submachine guns, it is a useful caliber for suppressed weapons as it lacks the sonic boom inherent to supersonic rounds.